Differential effects of interleukin 12 and interleukin 10 on superantigen-induced expression of cutaneous lymphocyte-associated antigen (CLA) and alphaEbeta7 integrin (CD103) by CD8+ T cells

At both cutaneous and mucosal sites, interleukin (IL)-10, IL-12 and transforming growth factor (TGF)-beta are important regulators of chronic inflammatory disease, where cutaneous lymphocyte-associated antigen (CLA) and alphaE integrin (CD103) may be expressed. Stimulation with streptococcal pyrogenic exotoxin C (SpeC) increased the expression of CD103 by CD8+ but not CD4+ T cells. While adding IL-12 augmented the expression of CLA, superantigen-induced expression of CD103 was markedly suppressed by IL-12, which could be reversed by TGF-beta. Antibodies against TGF-beta inhibited, and a combination of anti-TGF-beta and IL-12 completely abrogated the induced CD103 expression. IL-10 strongly decreased the frequency of CLA+ and although not increasing the frequency of CD103+CD8+ T cells, the amount of CD103 expressed per cell was markedly increased. Thus, the expression of CLA and CD103 may be antagonistically regulated by IL-10 and IL-12 and the balance between these cytokines could influence the T cell migration of inflammatory cells into epithelial tissues.     

Suppression of Experimental Autoimmune Myasthenia Gravis After CD8 Depletion is Associated with Decreased IFN-γ and IL-4

CDS⁺ T cells can perform both Th1 - and Th2-like functions by producing cytokines such as interferonγ (IFN-γ) and interleukin-4 (IL-4), as well as the immune response down-regulating transforming growth factor-β (TGF-β), which are all involved in the development of experimental autoimmune myasthenia gravis (EAMG), a model for human MG. We have reported that depletion of CD8⁺ T cells results in the suppression of EAMG accompanied by the down-regulation of AChR-specific B cell responses and AChR-reactive IFN-γ secreting Th1-like cells. To identify the involvement of IFN-γ, IL-4 and TGF-β in the development of EAMG after CD8⁺ T cell depletion, the expression of mRNA for these cytokines was studied in mononuclear cells from popliteal, inguinal and mesenteric lymph nodes, spleen and thymus by adopting in situ hybridization with complementary DNA oligonucleotide probes. Depletion of CD8⁺ T cells resulted in decreased levels of IFN-7 and IL-4 mRNA expressing cells in different lymphoid organs except thymus, but no change in the numbers of TGF-β mRNA expressing cells. The results imply that the suppression of EAMG after depletion of CD8⁺ T cells is caused by decreasing the effector factors but not by increasing the suppressor factor(s).     

The Effects of Mitogens, IL-2 and Anti-CD3 Antibody on the T-Cell Receptor Vβ Repertoire

Phytohaemagglutinin (PHA), Concanavalin A (Con A), interleukin-2 (IL-2), and monoclonal antibodies to CD3 (CD3MoAbs) are used for the assessment of the T-cell receptor (TCR) BV gene family expression in autoimmune disorders and multiple sclerosis, and to produce clones for assessment of cytokine profiles in progressive human immunodeficiency virus infection. The authors examined the effects of these stimulants on the TCR Vβ repertoire of resting and blastic CD4⁺ and CD8⁺ normal human peripheral blood lymphocytes, using three-colour cytofluorometry and a panel of anti-TCR Vβ monoclonal antibodies. IL-2 was associated with an increased percentage of blastic CD4⁺ cells expressing V_β5.1 (from median of 3.7% to 8.0%, P  = 0.0002) and blastic CD8⁺ cells expressing V_β5.3 (1.0 to 1.5%, P  = 0.0039). CD3MoAb caused a slight increase in V_β6.7 + blastic CD4⁺ cells (4.5 to 6.9%, P  = 0.0078). PHA did not alter the Vβ repertoire of blastic cells. Con A caused skewing in CD8⁺ blastic cells, toward expression of V_β5.2/5.3 (3.1 to 8.1%) and V_β5.3 (0.8 to 4.8%) ( P  = 0.0020). Thus, IL-2 stimulation causes slight alterations in the Vβ repertoire that should be taken into account in certain research settings. Con A produced skewing in CD8⁺ blastic cells suggesting that, in the presence of CD8, either Con A binds selectively to certain Vβ or the three-dimensional complex created by Con A's binding to other T-cell surface molecules induces preferential V_β5 stimulation.     

Characterization of T-Cell Receptor Vβ Repertoire in Ovarian Tumour-Reacting CD3+ CD8+ CD4− CTL Lines

T cells from tumour infiltrating lymphocytes (TIL) cultured in media containing IL-2 were shown to mediate in vitro and in vivo antitumour responses. To characterize the T-cell antigen receptor (TCR) Vβ expression in autologous cytotoxic effectors we isolated CD3⁺ CD8⁺ CD4⁻ cells from cultures of TIL and tumour-associated lymphocytes (TAL) and analysed the TCR Vβ repertoire of CD3⁺ CD8⁺ CD4⁻ lines of known HLA-A, -B and -C phenotype, using polymerase chain reaction (PCR). These lines showed preferential lysis of autologous tumours and lysed, to a much lesser extent, NK and LAK cellsensitive targets. Tumour lysis was inhibited by antibodies to CD3 and MHC class I antigens indicating that they are cytotoxic T lymphocytes (CTL). These CD8⁺ CTL lines expressed a broad distribution of TCR Vβ repertoire which was dominated by particular groups of Vβ families in each CTL line. However, no predominant expression of one or the same Vβ segment in all CTL lines was observed although statistical correlations between Vβ family usage and magnitude of the antitumour cytolytic response were found. These results suggest that certain TCR Vβ families may be selected by antigen in ovarian tumour-reactive T cells and this selection may be affected by Ag expression, and/or host factors. To our knowledge, this is the first documentation of TCR Vβ repertoire of human ovarian tumour-reactive CD3⁺ CD8⁺ CD4⁻ CTL from different individuals of known HLA types.     

Control of T-cell activation by CD4+ CD25+ suppressor T cells

Summary: Depletion of the minor (∼10%) subpopulation of CD4⁺ T cells that co-expresses CD25 (interleukin (IL)-2 receptor α-chain) by thymectomy of neonates on the third day of life or by treatment of adult CD4⁺ T cells with anti-CD25 and complement results in the development of organ-specific autoimmunity. Autoimmune disease can be prevented by reconstitution of the animals with CD4⁺ CD25⁺ cells. CD4⁺ CD25⁺-mediated protection of autoimmune gastritis does not require the suppressor cytokines IL-4, IL-10, or transforming growth factor (TGF)-β. Mice that express a transgenic T-cell receptor (TCR) derived from a thymectomized newborn that recognizes the gastric parietal cell antigen H/K ATPase all develop severe autoimmune gastritis very early in life. CD4⁺ CD25⁺ T cells are also powerful suppressors of the activation of both CD4⁺ and CD8⁺ T cells in vitro . Suppression is mediated by a cell contact-dependent, cytokine-independent T–T interaction. Activation of CD4⁺ CD25⁺ via their TCR generates suppressor effector cells that are capable of non-specifically suppressing the activation of any CD4⁺ or CD8⁺ T cell. Activation of suppressor effector function is independent of co-stimulation mediated by CD28/CTLA-4 interactions with CD80/CD86. We propose that CD4⁺ CD25⁺ T cells recognize organ-specific antigens, are recruited to sites of autoimmune damage where they are activated by their target antigen, and then physically interact with autoreactive CD4⁺ or CD8⁺ effector cells to suppress the development of autoimmune disease.     

Natural CD4+ CD25+ regulatory T cells. Their role in the control of superantigen responses

Summary: CD4 regulatory T cells have a major role in controlling the immune response to self and foreign antigens. Natural CD4⁺ CD25⁺ T cells are a major component of the regulatory subset. Their absence is associated with the development of autoimmune and inflammatory diseases and with abnormal peripheral T-cell homeostasis. Two main characteristics discriminate natural CD4⁺ CD25⁺ T cells from their CD4⁺ CD25⁻ counterparts, namely their cytokine production profile and their behavior during tolerance induction. Natural CD4⁺ CD25⁺ T cells produce interleukin (IL)-10, a cytokine that contributes to their regulatory role. They do not produce IL-2 and are dependent on exogenous IL-2 for proliferation in vitro and in vivo . Studies of their response to superantigen administration in vivo show that they are resistant to clonal deletion but can be tolerized by anergy. Their resistance to apoptosis may contribute to their continuous regulatory function, as it allows them to maintain permanent control over effector T cells.     

Lymphocytic Choriomeningitis Virus Infection is Associated with Long-Standing Perturbation of LFA-1 Expression on CD8+ T Cells

Flow cytometric analysis of splenocytes from mice infected with lymphocytic Choriomeningitis virus revealed marked and long-standing up-regulation of LFA-1 expression on CD8⁺, but not on CD4⁺ T cells. Appearance of CD8⁺ T cells with a changed expression of adhesion molecules reflected polyclonal activation and expansion which was demonstrated not to depend on CD4⁺ T cells or their products. Cell sorting experiments defined virus-specific CTL to be included in this population (LFA-1^hiMEL-14^lo), but since about 80% of splenic CD8⁺ T cells have a changed phenotype, extensive bystander activation must take place; this is indicated also by the finding that CD8⁺LFA-l^hi cells transiently express several markers of cellular activation, e. g. transferrin receptor, IL-2Rα and β. Analysis of cells from the cerebrospinal fluid of mice infected intracerebrally showed that virtually all T cells present belonged to the CD8LFA-lhi subset and, correspondingly, the ligand ICAM-1 was found to be up-regulated on endothelial cells in the inflamed meninges. Preincubation of LCMV-primed donor splenocytes with anti-LFA-1 markedly inhibited the transfer of virus-specific delayed-type hypersensitivity to naive recipients. Together, these findings indicate that up-regulation of LFA-1 expression is a critical factor involved in directing activated CD8⁺ T cells to sites of viral infection.     

Control of intestinal inflammation by regulatory T cells

Summary: Transfer of CD4⁺ T cells to immune-deficient mice in the absence of the CD25⁺ subset leads to the development of colitis, indicating that regulatory cells capable of controlling a bacteria-driven inflammatory response are present in normal mice. Cells with this function are present in the thymus as well as in the periphery of germ-free mice, suggesting they may be reactive with self-antigen. These cells resemble CD4⁺CD25⁺ cells that inhibit organ-specific autoimmunity, suggesting that a similar subset of regulatory T cells may control responses to self and foreign antigens. Development of colitis is dependent on accumulation of activated CD134L⁺ dendritic cells (DC) in the mesenteric lymph nodes, which is inhibited by CD4⁺CD25⁺ cells, indicating that regulatory T cells may control DC activation in vivo . Whilst inhibition of T-cell activation in vitro by CD4⁺CD25⁺ cells does not involve interleukin-10 and transforming growth factor-β, these cytokines are required for the suppression of colitis. It may be that control of responses that activate the innate immune system requires multiple mechanisms of immune suppression. Recently, we identified CD4⁺CD25⁺ cells with immune suppressive activity in the thymus and peripheral blood of humans, raising the possibility that dysfunction in this mechanism of immune regulation may be involved in the development of autoimmune and inflammatory diseases.     

Multiple Sclerosis: IFN-β Induces CD123+BDCA2– Dendritic Cells that Produce IL-6 and IL-10 and have No Enhanced Type I Interferon Production

IFN-β, an approved drug for multiple sclerosis (MS), acts on dendritic cell (DC) by suppressing their production of IL-12p40 and increasing IL-10. This results in Th2-biased immune responses. The nature of IFN-β-modulated DC remains elusive. Previously, we observed that IFN-β dose dependently induces expression of CD123, i.e. a classical marker for plasmacytoid DC, on human blood monocyte-derived myeloid DC. Such IFN-β-modulated DC produce predominantly IL-10 but are IL-12 deficient, with potent Th2 promotion. In the present study, we further characterize IFN-β-modulated DC by using recently identified blood DC antigens (BDCA) and investigate their ability to produce Type I IFN in response to virus stimulation. We show that IFN-β induces development of CD123⁺ DC from human blood monocytes, which coexpress BDCA4⁺ but are negative for BDCA2^–, a specific marker for plasmacytoid DC. Such IFN-β-modulated DC produce large amounts of IL-6 and IL-10, but no IL-12p40 and have no enhanced IFN-β and IFN-β production. The findings indicate that IFN-β-modulated DC represent a myeloid DC subset with diminished CD11c, BDCA-1 and CD1a expression, having potent Th2-promoting function but lacking antiviral capacity.     

Restricted and Individual Usage of T-cell Receptor β-Gene Variables in Nickel-Induced CD4+ and CD8+ Cells

Nickel allergy is manifested as contact allergic eczema elicited by delayed-type hypersensitivity, the reaction being mediated by T lymphocytes. We examined the T-cell receptor (TCR) β-chain variable gene segment (Vβ) use of nickel-induced CD4⁺ and CD8⁺ T cells in the peripheral blood of nickel-sensitive and non-sensitized subjects. The results show that each patient had an individual Vβ repertoire overexpressed, these being in CD4⁺ cells Vβ10 and Vβ13 (in subject A); Vβ1, Vβ2, Vβ13 and Vβ21 (subject B); Vβ1 and Vβ10 (subject C); Vβ9 and Vβ19 (subject D). Thus, no single Vβ gene dominated in a majority of the CD4⁺ samples. The Vβ genes overexpressed in patient CD8⁺ nickel-induced T cells were Vβ1 (in subject A), Vβ1 (subject B), Vβ1 and Vβ2 (subject C) and Vβ7 (subject D), domination of Vβ1 being seen in most of the CD8⁺ samples (75%). No specific overexpression of any Vβ genes in the nickel-allergic subjects was found in comparison with the non-sensitized subjects. In conclusion, an individual pattern of restricted Vβ genes was induced with nickel in CD4⁺ and CD8⁺ T cells in each nickel allergy patient.     

Vβ Usage and T Regulatory Cells in Children Following Partial or Total Thymectomy after Open Heart Surgery in Infancy

During open heart surgery in infants the thymus was usually removed, partly or completely. Our previous studies on 16 such children indicated reduced T-cell output later in life with signs of extrathymic maturation of the T cells, but no reduction in T regulatory cells (CD4⁺CD25⁺). The diversity of the T-cell repertoire in these children was examined to test if the extrathymic microenvironment could alter Vβ usage. The expression of Foxp3 and CD127 in CD4⁺CD25^high T cells was measured in order to determine whether the T regulatory cells had the phenotype of natural T regulatory cells. There was a wide distribution of Vβ usage in both study and control groups. Significant variability was found in Vβ usage for CD4⁺ and CD8⁺ T cells when the distribution of the percentage of T cells expressing each Vβ family was analysed between individuals within each group ( P  < 0.001; Kruskal–Wallis). Significant difference was also found in average usage of Vβ2, Vβ5.1 and Vβ14 chains within CD4⁺ T cells and Vβ2, Vβ8 and Vβ21.3 chains within CD8⁺ cells between the groups ( P  < 0.05; Student's t -test). There was no difference between the two groups with regard to the proportion of CD4⁺CD25^high T cells and no difference in the average expression of Foxp3 or CD127 within the CD4⁺CD25^high population. Our data provide evidence that cardiothoracic surgery in infants and total or partial thymectomy alters Vβ usage, suggesting more limited selection in such children than in the control group. The frequency of natural T regulatory cells seems to be unimpaired.     

Primary Stimulation of CD4+ Cells in the Presence of IL-4 or IFN-γ Alters the Frequencies of Cytokine-Producing Cells at Restimulation

The induction of specific effector functions in naive T cells may be directed by accessory signals during activation. These could be elicited through binding to cell surface molecules or through factors secreted by antigen-presenting cells or other simultaneously activated cells. We have investigated the influence of CD8⁺ cells and of exogenousiy added cytokines (interleukin (IL)-2, IL-4 and interferon (IFN)-γ) on the cylokine production in splenic CD4⁺ T cells. IL-2, IL-4, IL-5 and IFN-γ production in CD4⁺ cells was measured at the single cell level during primary mitogen stimulation in vitro in the presence or absence of factors or CD8⁺ cells. On day 5 the cells were restimulated with mitogen alone and analysed to evaluate the short-term development of cytokine-producing cells in such cultures. Preactivation in the presence of either exogenous IL-4 or IFN-γ led to an increased production of IL-4 and IFN-γ respectively at restimtilation, and the effects of both IL-4 and IFN-γ were augmented by IL-2. After preactivation in the presence of IL-2 and IL-4, every third CD4⁺ cell could be induced to produce IL-4. Exogenous IL-4 or IFN-γ further decreased each other's production. Depletion of CD8⁺ cells before activation resulted in a slight increase of IL-4-producing cells, indicating that simultaneous activation of CD8⁺ cells will influence lymphokine production in CD4⁺ cells. The results suggest that the pattern of lymphokines induced in naive cells may be influenced by factors secreted by preactivated CD4⁺ and CD8⁺ cells, and that naive cells are preferentially 'recruited' to produce similar cytokines.     

CD3−4−8− Thymocyte Precursors with Interleukin-2 Receptors Differentiate Phenotypically in Coculture with Thymic Stromal Cells

CD3⁻4⁻8⁻ interleukin-2 receptor positive (IL-2R⁺) thymocyte precursors from adult mice were cocultured with thymic stromal cells from syngeneic adult mice. The IL-2R⁺CD3⁻4⁻8⁻ thymocytes were obtained by positive panning of IL-2R⁺ cells followed by either sorting or negative panning of triple negative cells, and they were cocultured with primary or secondary cultures of heterogeneous thymic stromal cells. Phenotypic maturation of these precursor cells was extremely rapid. Within 2½ days significant numbers of CD4⁺8⁺ and CD3⁺4⁺8⁻ cell populations developed, the latter expressing the αβ T-cell receptor (αβ-TCR). Thus heterogeneous stromal cell cultures support the development of IL-2R⁺ precursors and with these methods it will now be possible to isolate the particular stromal cells involved at each stromal-dependent step.     

In Vivo Activation of T-Cell Induction into the Primed Phenotype and Programmed Cell Death by Staphylococcal Enterotoxin B

The authors demonstrate that SEB immunization activates Vβ8⁺ T cells and induces the acquisition of the primed phenotype as defined previously by low MEL-14 and high Pgp-1 expression. SEB-activated spleen CD4⁺ and CD8Vβ8⁺ T cells have different population dynamics and regulate the expression of MEL-14 and Pgp-1 differentially, suggesting that the SEB-MHC class II complex preferentially activates CD4Vβ8⁺ T cells. Interestingly, at day 3 after SEB immunization, Vβ8⁺ T cells expressing low, but not high, levels of MEL-14 undergo apoptosis, indicating that T-cell activation is a prerequisite for triggering programmed cell death. These results might help to trace antigen-reactive cells to the activated or primed pool, as well as to identify those cells which will undergo programmed cell death.     

Effect of 12 Neutralizing Anti-Cytokine Antibodies on In Vitro Activation of B-Cells. Interleukin-12 is Required by B1a but not B2 Cells

Normal human peripheral blood mononuclear cells, depleted of most monocytes and virtually all CD8-positive cells, were stimulated in vitro with pokeweed mitogen plus Staphylococcus aureus Cowan I in the presence or absence of variousneutralizing anti-cytokine antibodies. Numbers of CD5⁺ and CD5⁻ immunoglobulin-secreting cells were determined using the protein A haemolytic plaque assay after labelling B1a cells with anti-CD5-coated beads. Antibodiesagainst IL-2, IL-5 and IL-10 had little or no effect on plaque-forming cell (PFC) induction; anti-IL-6, -TNFα and -TGFβ enhanced PFC induction; anti-IL-1α, -IL-1β, -IL-4, -IFNγ and -IL-13 suppressed PFC induction. B1a and B2 cells were equally affected by cytokine deprivation using these 11 neutralizing antibodies. In contrast, neutralizing anti-IL-12 suppressed induction of CD5⁺ but not CD5⁻ PFC. Furthermore, recombinant IL-12, if added during thefirst 48 h of culture, enhanced CD5⁺ PFC induction while marginally suppressing (IgG-) or not affecting (IgA-, IgM-) induction of CD5⁻ PFC. IL-12 did not preferentially increase survival in culture of B1a cells norinduce expression of CD5 on B2-cells. Further studies are required to determine whether manipulation of B1a and B2 subsets in vivo using IL-12 could be achieved in clinical situations where imbalances in the two populations have beenobserved.     

Phenotypical Characterization of Cells in the Thoracic Duct of Patients with and without Systemic Inflammatory Response Syndrome and Multiple Organ Failure

The subset composition and recirculation properties of the migrating lymphocyte pool in humans is largely unknown. The present study was conducted in order to phenotypically characterize cells in human thoracic duct lymph of patients under non-inflammatory and inflammatory conditions. These data were compared with data from peripheral blood, with special emphasis on those cells homing to the gut. Thoracic duct lymph and peripheral blood contained comparable proportions of B and T lymphocytes and CD8⁺ cells. Thoracic duct lymph contained proportionally more CD4⁺ cells, more CD4⁺CD45RO⁺ that express α₄β₇ cells and more CD8⁺CD45RO⁺ that express α₄β₇, as compared to peripheral blood. These data suggest an equal recirculation rate of B and T lymphocytes; a more active recirculation of CD4⁺ cells compared to CD8⁺ cells; and a more active recirculation of memory cells to the gut as compared to other extra-lymphoid sites in patients under non-inflammatory conditions. Data were also obtained in patients with the system inflammatory response syndrome and multiple organ failure. Although it is generally assumed that granulocytes and monocytes do not recirculate, lymph of multiple organ failure patients contained significantly more granulocytes than monocytes, indicating that in severe generalized inflammatory states these cells re-enter the circulation through the thoracic duct. Furthermore, no increased activation of cells homing to the gut was found in these patients.     

Rheumatoid Inflammatory T-Cell Clones express mostly Th1 but also Th2 and Mixed (Th0-Like) Cytokine Patterns

This study was performed in order to characterize whether T cells from rheumatoid synovial inflammation belong to the Th1- or Th2-like functional subsets. Cytokine production was studied in 26 CD4⁺αβ⁺ and 2 CD8⁺αβ T-cell clones from the synovial fluid, the synovial membrane and peripheral blood of 5 patients. Fifteen of the CD4⁺ clones were raised against various mycobacterial antigens and 11 CD4⁺ clones and 2 CD8⁺ clones were raised unspecifically using PHA and/or IL-2. The specificities of these clones are not known. In the mycobacterial antigen-specific group, all CD4⁺'αβ T-cell clones produced IFN-γ at high levels, while the production of IL-4 was generally absent or low (< 1 ng/ml), consistent with a Thl-like profile. Some of these clones, however, also produced various amounts of IL-10 which has been regarded as a Th2 product but can be produced also in lower amounts by Thi cells. One HSP-65-specific clone produced levels of IL-4 and IL-10 in the same order as that of IFN-γ, thus appearing to be Th0-like. Among the 11 unspecific CD4⁺ clones, 7 showed a Thl-like pattern but with lower levels of IFN-γ than the antigen-specific clones. However, three clones did not produce any IFN-γ activity but produced IL-4 and one of them also produced distinct amounts of IL-10, compatible with a Th2-like pattern. In addition, one of the clones also showed an almost equally strong IFN-γ and IL-4 production, thus most likely representing a Th0-like clone.     

Contrary Roles of IL-4 and IL-12 on IL-10 Production and Proliferation of Human Tumour Reactive T Cells

The cytokine profile of tumour reactive T cells is likely to play a central role in their function. However, little is known about how cytokine patterns of tumour reactive T cells can be regulated. Here, the authors investigated the influence of exogenous regulatory cytokines in addition to interleukin-2 (IL-2) on cytokine patterns and the proliferation of T cells recognizing an autologous sarcoma cell line. In this system, IL-4 and IL-12 showed the most polarizing influences on tumour reactive T cells. Exogenous IL-4 induced a predominant production of IL-4 while decreasing the interferon-γ (IFN-γ) and IL-10 production by tumour reactive T cells. It also stimulated the growth of tumour reactive CD4⁺ T cell clones. In contrast, IL-12 substantially increased the production of IL-10 and IFN-γ. This was accompanied by a growth inhibition of tumour reactive T cells. The growth of CD4⁺ tumour reactive T cells was also suppressed by exogenous IL-10. This study shows that cytokine patterns and proliferation tumour reactive T cells can be significantly influenced by exogenous cytokines and confirms the hypothesis of a negative feedback loop of IL-12 by the induction of IL-10 in the context of human tumour reactive T cells.     

Ig-Isotype Patterns of Primary and Secondary B Cell Responses to Plasmodium Chabaudi Chabaudi Correlate with IFN-γ and IL-4 Cytokine Production and with CD45RB Expression by CD4+ Spleen Cells

In this work, the authors analysed T and B lymphocyte subsets and cytokine production in the spleen of BALB/c mice during polyclonal lymphocyte activation (primary infection) and parasite-specific response to Plasmodium chabaudi chabaudi (secondary infection). The secondary response was evaluated in fully immunoprotected animals, 60 days after a chloroquine-cured infection. The authors observed that in polyclonal lymphocyte activation antibody-secreting cells of all isotypes increased, with predominance of IgG2a and IgG3 classes. At that time, IFN-γ was largely produced, but IL-4/IL-5 were just slightly enhanced. In mice re-infected after 60 days, the Ig-isotype pattern was restricted to IgG1 and only IL–4/IL-5 were produced. In both responses, however, the levels of IL-2 were greatly reduced, while those of IL-10 were enhanced to similar levels. The different involvement of Th1 and Th2 cells in both responses was confirmed through analysis of CD45RB expression by CD4⁺ cells. The authors observed that CD45RB^high cells were the major CD4⁺ subpopulation in primary infected mice, while CD45RB^low cells predominated in 60 days re-infected animals. Moreover, the great majority of activated (large) CD4⁺ cells in the primary infection belonged to the CD45RB^high subset, while after re-infection most of the CD4⁺ large had a CD45RB^low phenotype.     

Culture of Regulatory T-Cell Lines from Bronchial Mucosa

T lymphocytes play a major role in many immune responses. In the last decade, special focus has been on the function of Th1 and Th2 effector cells. Now the importance of regulatory CD4⁺CD25⁺ T cells in maintenance of the immunological homeostasis emerges. Sarcoidosis is a multisystem granulomatous disorder often affecting the lungs. The typical sarcoid granulomas consists of epitheloid cells, macrophages and lymphocytes, mainly CD4⁺ T cells of Th1 phenotype. We have cultured T cells from bronchial biopsies of patients with sarcoidosis as well as from controls in high levels of interleukin 2 (IL-2) and IL-4 and demonstrate spontaneously arising CD4⁺ CD25⁺ populations and high concentrations of IL-10 in these cultures. The main difference between cultures of sarcoid origin compared to controls is a very much higher concentration of the inflammatory cytokines IL-6 and TNF-α in cultures of sarcoid origin.