Profiles of Th1 and Th2 Cytokines after Primary and Secondary Infection by Schistosoma mansoni in the Semipermissive Rat Host

In contrast to most mouse strains, rats eliminate the primary schistosome burden around 4 weeks postinfection and subsequently develop protective immunity to reinfection. In rat schistosomiasis, we have shown predominant expression of a Th2-type cytokine response at the mRNA level after primary infection. In the present study, we showed a significant increase in interleukin-4 (IL-4) mRNA expression in inguinal lymph nodes early after a secondary infection. IL-5 mRNA expression showed a significant increase at days 2 and 4 postreinfection in the spleen and lymph nodes, respectively. We did not detect any gamma interferon (IFN-gamma) mRNA after a challenge infection. Analysis of cytokine secretion by stimulated spleen cells after a primary infection showed predominant expression of IL-4 with maximum production on day 21, accompanied by production of IL-5 from day 11 to day 67. A significant increase in IFN-gamma secretion was detected at day 21. Analysis of immunoglobulin G2b (IgG2b) and IgG2c (Th1-related isotypes) showed undetectable levels of IgG2b, but detectable levels of specific IgG2c antibodies were observed from day 42. The analysis of Th2-related isotypes showed high specific IgG1 and IgG2a antibody titers from day 29. After a secondary infection, only IL-4 and IL-5 secretion was sustained. This is supported by the increased production of Th2-related isotypes. These findings showed that S. mansoni infection can drive Th2 responses in rats in the absence of egg production which is required to induce a Th2 response in mice and are in favor of the role of Th2-type cytokines in protective immunity against reinfection.     

T-helper type-1-dominated lymph node responses induced in C57BL/6 mice by optimally irradiated cercariae of Schistosoma mansoni are down-regulated after challenge infection.

Following a single percutaneous vaccination with optimally irradiated cercariae of Schistosoma mansoni, C57BL/6 mice mount a T-helper type-1 (Th1) lymphocyte-dominant immune response and are highly resistant to challenge infection. In this study, we show that, besides interferon-gamma (IFN-gamma), lymph node (LN) cells draining the site of vaccination produce significant amounts of interleukin (IL)-4 and IL-10 in culture with parasite antigen. After a challenge infection at the original site of vaccination, these LN cells did not generate an anamnestic Th1 response. Paradosically, IFN-gamma production and cell proliferation were profoundly down-regulated, whereas IL-4 production was enhanced and occurred earlier than in challenge control cultures. When challenge was applied to a site remote from vaccination, IFN-gamma down-regulation was less evident, but the IL-4 response was consistently enhanced. Neutralization of IL-10 in vitro restored IFN-gamma production by LN cells, whilst IL-4 levels were reduced. These data indicate that down-regulation of IFN-gamma is controlled by IL-10 and/or IL-4. Mice showing down-regulated Th1 responses in the LN after S. mansoni challenge infection did not have a reduced ability to eliminate challenge parasites, indicating that the post-vaccination Th1 response had already armed the lungs with effector T cells before administration of challenge parasites. The observed phenomena of down-regulated Th1 and enhanced Th2 responses may be of relevance to other systems involving multiple infections or vaccination/boosting. Repeated applications to percutaneous sites having common lymphatic drainage would be expected to favour Th2 responses. Alternatively, in order to induce Th1-dominant responses and avoid unwanted IL-4/IL-10 induction, the use of remote sites is indicated.     

Cytokine production in whole blood cultures from a fishing community in an area of high endemicity for Schistosoma mansoni in Uganda: the differential effect of parasite worm and egg antigens

The human host is continuously exposed to the egg and the adult worm developmental stages of Schistosoma mansoni during chronic infections with the parasite. To assess the cytokine responses induced by these different costimulating stages and how they are influenced by host age and infection intensity, whole blood samples from a cross-sectional cohort of 226 members of a Ugandan fishing community who had been resident in an area with high transmission of S. mansoni for the previous 10 years or from birth were stimulated with S. mansoni egg antigen (SEA) or worm antigen (SWA). SWA-specific gamma interferon (IFN-gamma) production increased with age, and the levels of SWA- and SEA-specific interleukin 3 (IL-3) were weakly correlated with schistosome infection intensity. The production of most cytokines was little affected by age or infection intensity but was either SEA or SWA specific. One hundred thirty-two members of the cohort coproduced IL-5 and IL-13 specifically in response to SWA, whereas only 15 produced these cytokines, and at much lower levels, in response to SEA. IL-10, IL-4, and IFN-gamma were also produced in response to SWA, whereas the response to SEA consisted almost exclusively of IL-10. Our results suggest that, in contrast to what has been described for the murine model of S. mansoni and during acute human infections, chronic intense exposure to and infection with S. mansoni in this cohort resulted in very low levels of response to SEA in vitro in the presence of a vigorous and mixed Th1-Th2 response to SWA.     

Anti-interleukin-4 modulation of the Th2 polarized response to the parasitic nematode Brugia pahangi.

Lymphatic filariasis is a chronic disease characterized by a pronounced Th2 bias in the immune response and impaired antigen (Ag)-specific Th1 responses. We have used a mouse model of filariasis to investigate the role of the infective form (the third-stage larvae [L3]) in modulating the immune response. Subcutaneous infection of BALB/c mice with L3 of Brugia pahangi has a profound effect on Th cell function. By day 12 post-infection, spleen cells from these mice exhibited a dramatic reduction in concanavalin A-driven proliferation and interleukin-2 (IL-2) and gamma interferon (IFN-gamma) secretion in comparison with uninfected controls. However, exposure to L3 did not render the mice completely unresponsive; these animals mounted a strong Th2 response to the parasite, characterized by elevated levels of IL-4, IL-5, and IL-10 and parasite-specific serum immunoglobulin G (IgG), IgG1, and IgE. Treatment of spleen cells from L3-infected mice with neutralizing anti-IL-4 or recombinant IL-2 resulted in a dramatic increase in concanavalin A-induced proliferation and IL-2 and IFN-gamma production. Despite their defective polyclonal Th1 response, cells from L3 infected mice proliferated when stimulated with Ag, and this response was blocked by anti-IL-4. However, anti-IL-4 treatment failed to induce Ag-specific IL-2 or IFN-gamma production, indicating that B.pahangi-primed Th1 cells do not appear to be present or are still unable to respond even in the absence of IL-4.     

The initial immune response during experimental cysticercosis is of the mixed Th1/Th2 type

The immunological events that occur during the initial stages of experimental cysticercosis are not known. The studies presented here examined the cytokines produced by peritoneal exudate cells (PECs), splenocytes and mesenteric lymph node (MLN) cells during the first week of infection with larval Taenia crassiceps in BALB/cJ mice. Proliferation assays determined that the earliest time when antigen-specific responses could be measured was 5 days post-infection. Concanavalin A (ConA) stimulation of host cells elicited an initial burst of IL-4 production at 24 h of infection and ConA-stimulated Th2-type cytokine production is predominant by 7 days post-infection. Thus, there are responses at day 1 of infection that seem to promote a Th2-type response. Stimulation of MLN cells, splenocytes and PECs with larval antigens supported previous reports of mixed Th1/Th2-type cytokine production with increases in interleukin (IL)-4, IL-10 and interferon (IFN)-gamma. Ex vivo IFN-gamma production by PECs from infected mice was increased at 3, 5 and 7 days post-infection, whereas at these times reduced ex vivo IL-10 production was observed. This ex vivo IFN-gamma response preceded an increasing IL-10 production by PECs between 3 and 7 days post-infection in parasite-specific and ConA-induced proliferation assays. Thus, infection with larval T. crassiceps results in an initial response mediated by IFN-gamma that is quickly followed by an increase in IL-10 production and subsequent reduction in the amount of IFN-gamma being produced.     

Endogenous IL-10 regulates IFN-gamma and IL-5 cytokine production and the granulomatous response in Schistosomiasis mansoni-infected mice.

In murine Schistosomiasis mansoni circumovum, granuloma formation is regulated by pro- and anti-inflammatory cytokines. Among the latter, interleukin-10 (IL-10) has been shown to regulate the inflammatory response. In this study we examined the role of endogenously produced IL-10 in T-helper 1 (Th1)- and Th2-type cytokine production and granuloma formation. The dynamics of IL-10 production through the course of the infection were different in granuloma versus splenic cells. In the former, production peaked during the early developmental stage (6 weeks of infection) of the granuloma and then declined. In splenocytes production peaked at 12 weeks, before down-modulation of the granuloma response. In the developing granuloma both macrophages and T cells secreted IL-10. In anti-IL-10 monoclonal antibody (mAb)-supplemented granuloma cell cultures endogenous IL-10-mediated regulation of interferon-gamma (IFN-gamma) was manifest only at 6 weeks; that of IL-2 continued throughout the infection (6-20 weeks). IL-4 production was unaffected, but IL-5 production was regulated at the 6 and 8 weeks time point. Splenocytes showed regulation of IFN-gamma and IL-2 production at the peak of the granulomatous response (8 weeks). IL-4 production was not regulated, whereas IL-5 production was regulated only at 6 weeks. Repeated injections of anti-IL-10 mAb given to mice at 6, 12 or 20 weeks of the infection significantly enhanced liver and lung granuloma growth, tissue eosinophilia, and IFN-gamma, IL-5 production at the early developmental phase (6 weeks) of the lesions. Thus, in schistosome-infected mice endogenous IL-10 is shown to regulate Th1- and Th2-type cytokine production and granuloma formation during the early Th0/Th1 phase of the immune response.     

Expression of interleukin-9 leads to Th2 cytokine-dominated responses and fatal enteropathy in mice with chronic Schistosoma mansoni infections

Mice infected with Schistosoma mansoni develop Th2 cytokine-mediated granulomatous pathology that is focused on the liver and intestines. In this study, transgenic mice constitutively expressing IL-9 were infected with S. mansoni and the outcome of infection was determined. Eight weeks after infection, transgenic mice with acute infections had a moderate increase in Th2 cytokine production but were overtly normal with respect to parasite infection and pathological responses. Transgenic mice with chronic infections died 10 weeks after infection, with 86% of transgenic mice dead by week 12 of infection, compared to 7% mortality in infected wild-type mice. Stimulation of mesenteric lymph node cells from infected transgenic mice with parasite antigen elicited elevated interleukin-4 (IL-4) and IL-5 production and reduced gamma interferon and tumor necrosis factor alpha production compared to the responses in wild-type mice. Morbid transgenic mice had substantial enlargement of the ileum, which was associated with muscular hypertrophy, mastocytosis, eosinophilia, goblet cell hyperplasia, and increased mucin expression. We also observed that uninfected transgenic mice exhibited alterations in their intestines. Although there was hepatic mastocytosis and eosinophilia in infected transgenic mice, there was no hepatocyte damage. Death of transgenic mice expressing IL-9 during schistosome infection was primarily associated with enteropathy. This study highlights the pleiotropic in vivo activity of IL-9 and demonstrates that an elevated Th2 cytokine phenotype leads to death during murine schistosome infection.     

Down-regulation of interleukin-12, interleukin-12R expression/activity mediates the switch from Th1 to Th2 granuloma response during murine Schistosomiasis mansoni

In murine schistosomiasis mansoni the worm egg-induced granulomatous inflammation is bi-phasic: an initial Th1 type is subsequently switched to a Th2 type response. Analysis of the cellular, molecular base of the Th1-associated response (5-6 weeks post infection) revealed mRNA messages for interleukin (IL)-12 p40, IL-12Rbeta2 and interferon (IFN)-gamma in the granulomatous livers. When the Th2 type granulomas matured (8 weeks post infection) message expression weakened or became extinct. Macrophages of the Th1 type granulomas produced maximal amounts of IL-12, but production diminished in the mature granulomas. A similar pattern of IL-12 responsiveness of granuloma lymphocytes was observed. In vitro IL-12 production by Th1 type granuloma macrophages was enhanced by tumour necrosis factor (TNF)-alpha and IFNgamma, whereas lymphocyte IL-12 responsiveness was boosted only by TNF-alpha. Both systems were down-regulated by IL-4 and IL-10 cytokines. Treatment of mice with anti-IL-10 monoclonal antibodies (MoAb) between 6 and 7 weeks of the infection enhanced mRNA expression for IFN-gamma and IL-12Rbeta2, but not for IL-12 p40. It is concluded that IL-12 and IL-12R expression and function regulate the Th1 phase of the liver granulomatous response. This phase is cross-regulated by type-2 cytokines especially IL-10.     

Increased Th1 and Th2 allergen-induced cytokine responses in children with atopic disease

BACKGROUND: Polyclonal cytokine responses following stimulation of T cells with mitogens or superantigens provides information on cytokine production from a wide range of T cells. Alternatively allergen-induced T cell responses can provide information on cytokine production by allergen-reactive T cells. While there is evidence of increased Th2 and reduced Th1 cytokine production following T cell stimulation with non-specific mitogens and superantigens, the evidence that Th1 cytokine production to allergens is decreased in line with a postulated imbalance in Th1/Th2 responses is unclear, with studies finding decreased, no difference or increased IFN-gamma responses to allergens in atopic subjects. OBJECTIVE: To examine childhood polyclonal and allergen-induced cytokine responses in parallel to evaluate cytokine imbalances in childhood atopic disease. METHODS: PBMC cytokine responses were examined in response to a polyclonal stimulus, staphylococcal superantigen (SEB), in parallel with two inhalant allergens, house dust mite (HDM) and rye grass pollen (RYE), and an ingested allergen, ovalbumin (OVA), in (a) 35 healthy children (non-atopic) and (b) 36 children with atopic disease (asthma, eczema and/or rhinitis) (atopic). RESULTS: Atopic children had significantly reduced IFN-gamma and increased IL-4 and IL-5 but not IL13 production to SEB superantigen stimulation when compared with non-atopic children. HDM and RYE allergens stimulated significantly increased IFN-gamma, IL-5 and IL-13, while OVA stimulated significantly increased IFN-gamma production in atopic children. CONCLUSION: We show that a polyclonal stimulus induces a reduced Th1 (IFN-gamma) and increased Th2 (IL-4 and IL-5) cytokine pattern. In contrast, the allergen-induced cytokine responses in atopic children were associated with both increased Th1 (INF-gamma) and Th2 (IL-5 and IL-13) cytokine production. The increased Th1 response to allergen is likely to reflect prior sensitization and indicates that increases in both Th1 and Th2 cytokine production to allergens exists concomitantly with a decreased Th1 response to a polyclonal stimulus in atopic children.     

IPSE/alpha-1: a major immunogenic component secreted from Schistosoma mansoni eggs

During infection with Schistosoma mansoni the egg stage of this parasite modulates the initial T helper (Th1) response into a Th2 response. This suggests that schistosome eggs contain factors responsible for that effect. We have recently described a glycoprotein (IPSE) from S. mansoni eggs that has a potent IL-4-inducing effect on human basophils. Here we demonstrate that IPSE is identical to a previously described molecule, the S. mansoni egg antigen alpha-1. We furthermore show that the expression of IPSE/alpha-1 at the level of both mRNA and protein is restricted to the egg stage. IPSE/alpha-1 is produced in and released from the subshell area of the egg and comes into close contact with inflammatory cells recruited to the vicinity of the egg surface. In line with this IPSE/alpha-1 is one of three major S. mansoni egg glycoproteins that induce pronounced antibody responses. Its IL-4-inducing capacity, moreover, suggests that IPSE/alpha-1 plays a role in initiating the Th2 response induced by patent S. mansoni infections.     

Differential induction of helper T cell subsets during blood-stage Plasmodium chabaudi AS infection in resistant and susceptible mice.

The induction of T helper cell subsets during the course of non-lethal or lethal blood-stage Plasmodium chabaudi AS infection was investigated using inbred strains of mice which differ in the level of resistance to this intraerythrocytic parasite. Resistant C57Bl/6 mice experience a non-lethal course of infection characterized by moderate levels of both parasitaemia and anaemia and resolution of primary acute infection by 4 weeks, while susceptible A/J mice experience lethal infection with fulminant parasitaemia and severe anaemia. T helper subset function was assessed during infection by determining the kinetics of spleen cell production in vitro of the Th1-derived cytokine, interferon-gamma (IFN-gamma), and of the Th2-derived cytokine, IL-5, using sandwich ELISAs. Spleen cells from resistant C57Bl/6 mice were found to produce high levels of IFN-gamma within 1 week of infection in response to both the mitogen concanavalin A (Con A) and malaria antigen. Furthermore, CD4+ T cells were found to be the source of IFN-gamma while both CD4+ and CD8+ T cells were found to produce IL-5. Decreased IFN-gamma production after day 10 was concomitant with significant production of IL-5 between 2 and 3 weeks post infection. In contrast, spleen cells from susceptible A/J mice produced high levels of IL-5 within the first week of infection. In addition, these animals were found to have high serum levels of IL-5. These results, thus, confirm previous observations that resolution of primary blood-stage P. chabaudi infection occurs by sequential activation of Th1 CD4+ T cells followed by activation of the Th2 subset, and in addition, suggest that induction of a strong Th2 response early in infection may lead to a severe and lethal course of malaria.     

Cross-regulatory role of interferon-gamma (IFN-gamma), IL-4 and IL-10 in schistosome egg granuloma formation: in vivo regulation of Th activity and inflammation.

This study examined the relationship of IL-4, IL-10 and IFN-gamma with regard to the local granuloma (GR) and draining lymph node (LN) response to Schistosoma mansoni eggs. Synchronized GR were induced in naive and schistosome-infected mice at the vigorous (8 weeks) and late chronic (20 weeks) stages. In LN cultures, IL-10 and IFN production peaked on day 4 and was greatest for 8 week-infected mice. All GR cultures contained IFN, but compared with naive mice IL-10 production was accelerated at 8 weeks and abrogated at 20 weeks, consistent with expansion and abatement of Th2 activity. Cytokine neutralization was performed in egg-challenged, naive mice that were adoptively sensitized with lymphoid cells from 8 week-infected donors. GR size, GR macrophage tumour necrosis factor (TNF) production and egg antigen-elicited IL-2, IL-4, IL-5, IL-10 and IFN were examined on day 4 of GR formation. Anti-IFN augmented GR area by 40%, increased local IL-4 and IL-10, but decreased IFN and TNF production. In corresponding LN cultures, IFN decreased by about 50%, while IL-2, IL-4, IL-10 and IL-5 increased by nearly two-, four-, five- and six-fold, respectively. Anti-IL-10 did not affect GR size or GR cytokines, but abrogated GR area by 40%, along with a reduction in local IL-4 and TNF production. In LN, IL-4 depletion reduced IL-4 and IL-5 by 60-70% and increased IFN levels. These results support the notion of a cross-regulatory network in which IFN inhibits Th2 and IL-10 inhibits Th1 cells. IL-4 fosters Th2 cells differentiation in LN, but also performs a critical recruitment function in the eosinophil-rich schistosome egg-induced GR, whereas IFN contributes to enhanced GR macrophage function.     

Schistosome infection stimulates host CD4(+) T helper cell and B-cell responses against a novel egg antigen, thioredoxin peroxidase

Egg granuloma formation during schistosome infections is mediated by CD4(+) T helper (Th) cells sensitized to egg antigens; however, most of the relevant sensitizing egg antigens are still unknown. Here we show that schistosome thioredoxin peroxidase (TPx)-1 is a novel T- and B-cell egg antigen in schistosome-infected mice. CD4(+) Th cell responses to fractionated egg components identified a significant response against a 26-kDa antigen; a partial amino acid sequence of this antigen was found to be identical to that of Schistosoma mansoni TPx-1. The native TPx-1 elicited significant proliferative responses as well as gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-5 secretion in CD4(+) cells from 8.5-week-infected CBA and C57BL/6 mice. By comparison, recombinant TPx-1 elicited a smaller, more type 1-polarized response, with significant production of IFN-gamma and IL-2, less IL-5, and essentially no IL-4. In C57BL/6 mice the responses to TPx-1 were relatively more prominent than that directed against the major egg antigen, Sm-p40, whereas in CBA mice the reverse was true. B-cell responses were also monitored in infected C57BL/6, C3H, CBA, and BALB/c mice. All strains had significant antibody levels against the TPx-1 protein, but the most significant antibody production ensued following parasite oviposition. TPx-1 was localized in eggs and shown to be secreted by eggs. The identification of egg antigens is important to understand the specific basis of granuloma formation in schistosome infections and may prove to be useful in strategies to ameliorate pathological responses.     

Phenytoin promotes Th2 type immune response in mice

The effects of chronic administration of phenytoin, a common anticonvulsive drug, on immune responses were studied in mice. Anti-keyhole limpet haemocyanin (KLH) IgE antibody response after KLH-immunization was enhanced in phenytoin-treated mice. Proliferative responses of spleen cells induced with KLH, concanavalin A (ConA), lipopolysaccharide and anti-CD3 antibody were reduced in phenytoin-treated mice. Accessory function of spleen adherent cells on ConA-induced T cell proliferative response was reduced in phenytoin-treated mice. KLH-induced IL-4 production of spleen cells was enhanced, while IFN-gamma production was reduced in phenytoin-treated mice. In addition, production of IL-1 alpha, but not IL-6 and IL-12 by spleen adherent cells from phenytoin-treated mice was reduced. Natural killer cell activity was reduced in phenytoin-treated mice. These results suggest that phenytoin treatment preferentially induces a Th2 type response. We also observed that plasma ACTH and corticosterone levels were increased in phenytoin-treated mice, and speculated that phenytoin might act directly and indirectly, through HPA axis activation, on the immune system to modulate Th1/Th2 balance.     

Generation of rat Th2-like cells in vitro is interleukin-4-dependent and inhibited by interferon-gamma.

Differentiation of naive T cells into effector cells producing T helper type 1 (Th1) and Th2 cytokines is regulated by the presence of specific cytokines in the T-cell microenvironment. The effect of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) on Th1- and Th2-like cell development was investigated in cultures of mixed rat spleen cells. These cells were cultured for 4 days in medium containing concanavalin A (Con A) with or without additional IL-2, IFN-gamma or IL-4. The cells were then washed and their capacity to produce IL-4, IL-5 and IFN-gamma determined following stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. Freshly isolated cells stimulated with PMA and ionomycin expressed detectable levels of IL-4 and IL-5 mRNA as measured by a quantitative polymerase chain reaction (PCR) procedure and much higher levels of IFN-gamma mRNA. Cells cultured with Con A for 4 days, washed, and restimulated with PMA + ionomycin were unable to express detectable levels of IL-4 and IL-5 mRNA, but produced high levels of IFN-gamma mRNA. Addition of IL-4, or anti-IFN-gamma antibody, to Con A-driven splenocyte cultures restored the ability of restimulated cells to express IL-4 and IL-5. CD4+ T cells isolated from these cultures also showed an increased capacity to secrete IL-4 and IL-5 when anti-IFN-gamma and IL-4 were present in the culture medium. When cultured for 4 days with Con-A, IL-4 and anti-IFN-gamma splenocytes showed an increased capacity to proliferate in response to recombinant IL-2 and proliferated in response to IL-4 alone. IL-2 had no effect on cytokine production by cultured splenocytes. These results indicate that: (1) IL-4 is essential for the generation of Th2-like cells; (2) IFN-gamma inhibits IL-4 production by mixed spleen cells and suppresses generation of IL-4 responsive T cells; (3) in mixed spleen cell cultures mitogenic stimulation favours differentiation of naive rat T cells into effector cells expressing a Th1, and not Th2, cytokine profile.     

Leishmania donovani-reactive Th1- and Th2-like T-cell clones from individuals who have recovered from visceral leishmaniasis.

Infections in humans by Leishmania donovani parasites can result in a fatal disease, visceral leishmaniasis (VL), or in a self-limiting asymptomatic infection. In murine models of the infection employing Leishmania major, the course of the disease can be directed into a VL-like syndrome by interleukin-4 (IL-4)-producing Th2 cells, or cure may result by Th1 cells secreting gamma interferon (IFN-gamma). The present study examined the potential of human T cells to generate Th1 or Th2 responses to L. donovani. The profiles of IFN-gamma, IL-4, and lymphotoxin secretion after antigen stimulation were analyzed in a panel of L. donovani-reactive CD4+ human T-cell clones generated from individuals who had recovered from VL after antimonial treatment. Two of the T-cell clones produced large amounts of IL-4 without production of IFN-gamma, seven clones produced both IFN-gamma and IL-4, and eight produced only IFN-gamma. This is the first report of a Th1- and Th2-type response in human leishmaniasis. These results suggest that in analogy with murine models, there is a dichotomy in the human T-cell response to L. donovani infections. Preferential activation of IL-4-producing Th2-like cells may be involved in the exacerbation of human VL, whereas activation of IFN-gamma-producing Th1 cells may protect the host from severe disease. Identification of leishmanial antigens activating one or the other type of T cells will be important in the development of vaccines against leishmaniasis.     

Serum concentrations of GM-CSF and G-CSF correlate with the Th1/Th2 cytokine response in cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection

The inflammation in cystic fibrosis (CF) patients with chronic Pseudomonas aeruginosa lung infection is dominated by polymorphonuclear neutrophils (PMNs). There seems to be a relationship between the PMN-dominated inflammation, pronounced antibody production and a Th2-dominated response. Apart from mobilizing monocytes and PMNs from the bone marrow, GM-CSF, G-CSF and IL-3 select subsets of dendritic cells, which subsequently induce distinct Th responses. Therefore, the present study examines the correlation between the mobilizing cytokines in serum and the Th responses. The IFN-gamma and IL-4 production by peripheral blood mononuclear cells, and the concentrations of GM-CSF and G-CSF in serum as well as lung function, were determined in 37 CF patients with and 6 CF patients without chronic P. aeruginosa lung infection. The GM-CSF/G-CSF ratio correlated both with the IFN-gamma production and good lung function. In addition, an inverse correlation between IL-3 and IFN-gamma was observed. The results indicate involvement of endogenous GM-CSF, G-CSF and IL-3 in the skewed Th response in CF, and change to a Th1-dominated response might be achieved with GM-CSF treatment.     

Prenatal immune priming with helminth infections: parasite-specific cellular reactivity and Th1 and Th2 cytokine responses in neonates

The present investigation aimed to determine to what extent maternal helminth infection primes parasite-specific cellular responsiveness in neonates. Umbilical cord mononuclear blood cells (UCBC) and peripheral blood mononuclear cells (PBMC) from mothers proliferated in response to mitogenic stimulation with concanavalin A, as well as to bacterial Streptococcus pyogenes-derived (streptolysin O) and helminth-specific antigens of Necator americanus and Onchocerca volvulus. Cellular responses to Echinococcus multilocularis (Em) and Oesophagostomum bifurcum (Oes), helminth parasites not endemic in the study area, were absent (for Em) or very low (for Oes due to antigenic cross-reactivity). Cellular responsiveness to mitogen and antigens was higher in mothers than in their neonates. Several Th1-type (IL-2, IL-12, and IFN-gamma) and Th2-type (IL-5 and IL-10) cytokines were produced by UCBC from neonates and PBMC from mothers. Low levels of IFN-gamma were elicited by UCBC in response to helminth and bacterial antigens, while secretion of IL-2 was pronounced and similarly high in neonates and their mothers. Amounts of IL-5 produced by UCBC in response to bacterial SL-O and mitogenic stimulation (PHA) were low, but equivalent levels of IL-5 were induced by intestinal helminth and filaria-derived antigens in neonates and mothers. A pronounced production of IL-10 and IL-12 by UCBC was observed--spontaneous IL-10 and IL-12 secretion by UCBC was higher in neonates than by PBMC from mothers. Net amounts of IL-10 elicited by helminth antigens were similar, while net IL-12 in response to mitogen, and bacterial and helminth antigens was significantly higher in mothers than their offspring. Our results indicate that human maternal helminth infection does sensitize in utero for parasite-specific cellular responsiveness in offspring, and also activates specific production of several cytokines, and such children do not present a dominant expression of immunity of either Th1 or Th2.     

Sequential production of Th1 and Th2 cytokines in response to live bacillus Calmette-Guérin.

Causes of individual variation in susceptibility to mycobacterial diseases are only partly understood. An efficient cell-mediated immune response is crucial for resistance. Macrophages and T cells interact to eliminate the mycobacteria, partially through the effects of secreted cytokines. A vigorous anti-bacterial inflammatory response is sometimes accompanied by severe tissue damage, while immunosuppression leads to progressive infection. Here, live, attenuated Mycobacterium bovis, bacillus Calmette-Guérin (BCG), was used as a model antigen to study cytokine production at the single-cell level in response to mycobacteria. Peripheral blood mononuclear cells from healthy individuals were challenged in vitro and the kinetics and frequencies of cytokine-producing cells were studied by immunofluorescent visualization of intracellular cytokines. Fourteen cytokines were assayed; interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-1 receptor antagonist (IL-1ra), IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), TNF-beta and granulocyte-macrophage colony-stimulating factor (GM-CSF). A sequential production of T helper-1 (Th1) and T helper-2 (Th2) cytokines was induced by BCG. Early, at days 1-2 after stimulation, the response was dominated by monokines and a low IFN-gamma and TNF-beta production. At days 4-5 there was a marked production of Th1 lymphokines, with approximately 6% IFN-gamma+ cells, 4% TNF-beta+ cells and 2% IL-2+ cells. Late in the reaction, at days 10-12, a Th2 response with IL-4, IL-5 and IL-10 was detected, while the synthesis of Th1 lymphokines and monokines declined. Overall, our results provide further evidence of IFN-gamma as the major cytokine induced by mycobacteria in healthy individuals, but also suggest that Th2 cytokines participate in the response.     

Nickel-induced IL-10 down-regulates Th1- but not Th2-type cytokine responses to the contact allergen nickel

Whereas the involvement of Th1- and Th2-type cytokines in contact allergy to nickel (Ni) is well documented, the role of the regulatory cytokine IL-10 is less clear. We therefore investigated the impact of IL-10 on Ni-induced Th1- (IFN-gamma) and Th2-type (IL-4 and IL-13) cytokine responses in human peripheral blood mononuclear cells (PBMC). PBMC from 15 blood donors with reactivity to Ni (Ni-PBMC) and 8 control donors devoid of reactivity (control PBMC) were stimulated with Ni and the frequency of cytokine-producing cells and the levels of secreted cytokines were analysed by ELISpot (IL-4, IL-13 and IFN-gamma) and ELISA (IL-10, IL-13 and IFN-gamma), respectively. The Ni-induced response was further assessed in the presence of recombinant IL-10 (rIL-10) or neutralizing antibody to IL-10 and the phenotype of the Ni-specific cytokine-producing cells regulated by IL-10 was determined by cell depletion experiments. Ni induced IL-10 production in Ni-PBMC (mean, (range); 33.1 pg/ml (0-93.4 pg/ml)) but not control PBMC (2.2 pg/ml (0-14.9 pg/ml)) (P = 0.002). Ni also induced significant production of IL-4, IL-13 and IFN-gamma that correlated with the IL-10 response. Addition of rIL-10 down-regulated the Ni-induced production of all cytokines but with a more pronounced effect on IFN-gamma. However, neutralization of Ni-induced IL-10 enhanced the levels of IFN-gamma induced by Ni (P = 0.004) but did not affect the number of IFN-gamma-producing cells or the production of other cytokines. Cell depletion experiments suggested that the Ni-specific IFN-gamma (and Th2-type cytokine) producing cells were CD4(+) T cells. The impact of IL-10 on Ni-induced IFN-gamma responses by CD4(+) T cells suggests that an important role of IL-10 in vivo is to counteract the allergic reactions mediated by Th1-type cytokines.