CD4+ T cell help improves CD8+ T cell memory by retained CD27 expression

CD4+ T cell help during the priming of CD8+ T lymphocytes imprints the capacity for optimal secondary expansion upon re-encounter with antigen. Helped memory CD8+ T cells rapidly expand in response to a secondary antigen exposure, even in the absence of T cell help and, are most efficient in protection against a re-infection. In contrast, helpless memory CTL can mediate effector function, but secondary expansion is reduced. How CD4+ T cells instruct CD8+ memory T cells during priming to undergo efficient secondary expansion has not been resolved in detail. Here, we show that memory CTL after infection with lymphocytic choriomeningitis virus are CD27(high) whereas memory CTL primed in the absence of CD4+ T cell have a reduced expression of CD27. Helpless memory CTL produced low amounts of IL-2 and did not efficiently expand after restimulation with peptide in vitro. Blocking experiments with monoclonal antibodies and the use of CD27(-/-) memory CTL revealed that CD27 ligation during restimulation increased autocrine IL-2 production and secondary expansion. Therefore, regulating CD27 expression on memory CTL is a novel mechanism how CD4+ T cells control CTL memory.     

Interleukin-10 (IL-10) secretion in systemic lupus erythematosus and rheumatoid arthritis: IL-10-dependent CD4+CD45RO+ T cell-B cell antibody synthesis

Interleukin-10 (IL-10) is a major immunoregulatory cytokine and has a multitude of immunomodulatory effects in the immune system. In this study, we have examined the secretion andin vitro function of IL-10 in B cell hyperactivity in antibody production in two common autoimmune diseases, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). IL-10 was detectable in serum of all active SLE and serum and synovial fluid samples of all RA patients but in none of the normal controls. B cells and CD4+CD45RO+ memory T cells secreted highly enhanced levels of IL-10 in SLE and RA versus normals. Increased IgM and IgG production by B cells-CD4+CD45RO+ T cells in SLE and RA was IL-10 dependent, since neutralization of IL-10 cytokine by anti-IL-10 antibody drastically reduced Ig synthesis in these coculture experiments. B cell hyperactivity in autoantibody production in SLE and RA may be a function of IL-10-dependent CD4+CD45RO+ Th2 cell activation. Therefore, IL-10 may play an important role in highly disturbed immune system and B cell-T cell function in these immune disorders.     

IL-4Ralpha signaling is important for CD8+ T cell cytotoxicity in the absence of CD4+ T cell help

Cytotoxic CD8(+) T cells are key mediators of viral clearance during primary infection through their production of IFN-gamma and lysis of virally infected cells. Comparatively, the cytokines IL-4 and IL-13 are typically associated with the development of Th2 immune responses against allergens and parasites, while their influence on cytotoxic CD8(+) T cell responses is controversial. We have investigated the roles of IL-4 and IL-13 in the development of CD8(+) T cell responses against influenza infection. We show that in the absence of either IL-4 or IL-13, CD8(+) T cells proliferated and a normal secondary cytotoxic response developed in vitro. In striking contrast, the absence of IL-4Ralpha resulted in impaired ex vivo proliferation and consequently no secondary CTL activity, whereas the in vivo response appeared normal. We show that the presence of CD4(+) T cell help, or the addition of exogenous IL-2 in vitro, restored the response. Taken together, this work reveals previously unrecognized in vivo redundancies between IL-4, IL-13 and IL-2 during immune responses against influenza virus.     

CTLA-4 blockade reverses CD8+ T cell tolerance to tumor by a CD4+ T cell- and IL-2-dependent mechanism.

A tumor-specific CD8+ T cell response was studied using adoptive transfer of OT-I TCR transgenic cells. Upon i.p. challenge with E.G7 tumor, OT-I cells undergo CD4+ T cell-independent expansion at the tumor site and develop lytic function. Before tumor elimination, however, they leave the peritoneal cavity (PC) and appear in the LN and spleen where they exhibit "split anergy" and cannot further proliferate to antigen. Administering anti-CTLA-4 mAb early caused sustained OT-1 expansion in the PC, and late administration caused the OT-I cells to return to the PC and further expand; in both cases, tumor was controlled. These effects required CD4+ T cells and IL-2 and appear to result from reversal of the nonresponsive state of the CD8+ T cells.     

Fluticasone propionate increases CD4CD25 T regulatory cell suppression of allergen-stimulated CD4CD25 T cells by an IL-10-dependent mechanism

BACKGROUND: Corticosteroids are the most effective anti-inflammatory therapy for allergic diseases, and these drugs inhibit TH2 T-cell activation. We previously reported that CD4+CD25+ T cells from atopic donors suppressed allergen-stimulated T cells less than those from nonatopic donors. OBJECTIVE: We sought to determine the effect of fluticasone propionate (FP) on allergen-stimulated CD4+CD25- T cells and on the suppressive ability of CD4+CD25+ T cells. METHODS: CD4+CD25+ and CD4+CD25- T cells were separated from peripheral blood of atopic and nonatopic volunteers and cultured alone or mixed in the presence of allergen. Effects of FP were assessed by means of addition to cultures or preincubation with CD4+CD25+ T cells. RESULTS: FP inhibited allergen-stimulated proliferation of CD4+CD25- T cells in a dose-dependent manner. Preincubation of CD4+CD25+ T cells in FP increased subsequent suppressive activity of these cells in allergen-stimulated cultures with CD4+CD25- T cells. This effect was seen when cells were obtained from both nonatopic and atopic donors but was less for cells obtained from atopic individuals. Prior exposure of CD4+CD25+ T cells to FP also increased subsequent IL-10 production by these cells when stimulated with allergen, and addition of anti-IL-10 antibody reversed the steroid-induced enhancement of suppression in mixed cultures. CONCLUSION: Increased suppression by CD4+CD25+ T cells might play a role in anti-inflammatory effects of corticosteroids in asthma and allergic diseases.     

IL-10 production by CD4+ effector T cells: a mechanism for self-regulation

The development of Th1 lymphocytes is essential for cell-mediated immunity and resistance against intracellular pathogens. However, if left unregulated, the same response can cause serious damage to host tissues and lead to mortality. A number of different paracrine regulatory mechanisms involving distinct myeloid and lymphoid subpopulations have been implicated in controlling excessive secretion of inflammatory cytokines by Th1 cells. Much of this work has focused on interleukin (IL)-10, a cytokine with broad anti-inflammatory properties, one of which is to counteract the function of Th1 lymphocytes. While studying the role of IL-10 in regulating immunopathology during infection with the intracellular parasite Toxoplasma gondii, we discovered that the host-protective IL-10 derives in an autocrine manner from conventional interferon-γ (IFN-γ)-producing T-bet⁺ Foxp3^neg Th1 cells. In the following review, we will discuss these findings that support the general concept that production of IL-10 is an important self-regulatory function of CD4⁺ T lymphocytes.     

CD25+ CD4+ T cells compete with naive CD4+ T cells for IL-2 and exploit it for the induction of IL-10 production

Maintenance of homeostasis in the immune system involves competition for resources between T lymphocytes, which avoids the development of immune pathology seen in lymphopenic mice. CD25+ CD4+ T cells are important for homeostasis, but there is as yet no consensus on their mechanisms of action. Although CD25+ CD4+ T cells cause substantial down-regulation of IL-2 mRNA in responder T cells in an in vitro co-culture system, the presence of IL-protein can be demonstrated by intracellular staining. As a consequence of competition for IL-2, CD25+ CD4+ T cells further up-regulate the IL-2R alpha chain (CD25), a process that is strictly dependent on IL-2, whereas responder T cells fail to up-regulate CD25. Similarly, adoptive transfer into lymphopenic mice showed that CD25+ CD4+ T cells interfere with CD25 up-regulation on co-transferred naive T cells, while increasing their own CD25 levels. IL-2 sequestration by CD25+ CD4+ T cells is not a passive phenomenon but instead initiates--in conjunction with signals through the TCR--their differentiation to IL-10 production. Although IL-10 is not required for in vitro suppression, it is vital for the in vivo function of regulatory T cells. Our data provide a link explaining the apparent difference in regulatory mechanisms in vitro and in vivo.     

Age-related increase in the fraction of CD27-CD4+ T cells and IL-4 production as a feature of CD4+ T cell differentiation in vivo.

The influence of ageing on phenotype and function of CD4+ T cells was studied by comparing young (19-28 years of age) and aged (75-84 years of age) donors that were selected using the SENIEUR protocol to exclude underlying disease. An age-related increase was observed in the relative number of memory cells, not only on the basis of a decreased CD45RA and increased CD45RO expression, but also on the basis of a decrease in the fraction of CD27+CD4+ T cells. Our observation that the absolute number of CD45RO+CD4+ T cells was increased, while absolute numbers of CD27-CD4+ T cells remained unchanged in aged donors, indicates that the latter subset does not merely reflect the size of the CD45RO+CD4+ T cell pool. The increased fraction of memory cells in the aged was functionally reflected in an increased IL-4 production and T cell proliferation, when cells were activated with the combination of anti-CD2 and anti-CD28, whereas IL-2 production was comparable between both groups. No differences were observed with respect to proliferative T cell responses or IL-2 production using plate-bound anti-CD3 or phytohaemagglutinin (PHA). The observation that IL-4 production correlated with the fraction of memory cells in young donors but not in aged donors suggests different functional characteristics of this subset in aged donors.     

Induction of IL-10+CD4+CD25+ T cells by grass pollen immunotherapy

BACKGROUND: Immunotherapy involves the modulation of allergen-specific T-cell responses, either T(H)2-to-T(H)1 immune deviation or, in bee venom-treated patients, induction of IL-10 production by CD4+CD25+ T cells. IL-10-producing CD4+CD25+ regulatory T cells have emerged as potential mediators of immune tolerance in numerous murine models of immunopathology. OBJECTIVE: The aim of this study was to evaluate the role of IL-10 production and CD4+CD25+ T cells in the response to grass pollen immunotherapy. METHODS: PBMCs were isolated from patients after 1 year of grass pollen immunotherapy and from matched untreated atopic and healthy control subjects. After 6 days of in vitro stimulation with Phleum pratense, production of IL-10, IL-5, IL-4, and IFN-gamma and proliferation and numbers of CD4+CD25+ T cells were measured. T cells were then stimulated for a further 5 hours with phorbol 12-myristate 13-acetate and ionomycin and assessed for intracellular IL-10 by means of flow cytometry. RESULTS: Patients undergoing immunotherapy produced significantly more IL-10 than atopic control subjects (patients undergoing immunotherapy, 116 +/- 21 pg/mL [n = 11]; atopic patients, 30 +/- 5 pg/mL [n = 11]; P <.001), and the number of CD4+CD25+ cells identified after allergen stimulation was also greater in the immunotherapy group. The numbers of CD4+CD25+ T cells correlated positively with activation as measured by proliferation in both of the control groups but not in the immunotherapy group. Moreover, only T cells from patients undergoing immunotherapy were positive for intracellular IL-10, and these were almost exclusively CD4+CD25+ cells. CONCLUSION: Grass pollen immunotherapy results in a population of circulating T cells that express the IL-10(+) CD4+CD25+ phenotype in response to allergen restimulation.     

ICAM-1 costimulation induces IL-2 but inhibits IL-10 production in superantigen-activated human CD4+ T cells.

We have previously reported that costimulatory pathways including B7-CD28 and lymphocyte function-associated antigen-3 (LFA-3)-CD2 shape distinct activation profiles in human CD4+ T cells. We now show that superantigen (SAg), in combination with intracellular adhesion molecule-1 (ICAM-1) costimulation drives a proliferative response accompanied by high levels of interleukin-2 (IL-2) and moderate levels of interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF). This response profile differs from that observed in B7 or LFA-3 costimulated T cells because our previous results showed that B7-CD28 costimulation was accompanied by high levels of IL-2, IFN-gamma and TNF, whereas LFA-3 was a potent inducer of IFN-gamma and TNF, but had little influence on IL-2 production. The ICAM-1-induced IL-2 production could efficiently be abrogated with monoclonal antibody (mAb) against ICAM-1 or LFA-1, showing that the activation is dependent of a functional ICAM-1-LFA-1 pathway. SAg-induced IL-2, IFN-gamma and TNF were detected in both CD4+ and CD8+ T cells, whereas production of IL-10 was restricted to CD4+ T cells. A major finding in the present study was that ICAM-1 costimulation strongly inhibits IL-10 production in CD4+ T cells. Our data demonstrate that ICAM-1 costimulation is sufficient to induce large amounts of IL-2. The presence of ICAM-1 results in suppression of IL-10 production in T helper (Th) cells, which may favour the development of Th1 and not Th2 T cells.     

Marine peptides as immunomodulators: Californiconus californicus-derived synthetic conotoxins induce IL-10 production by regulatory T cells (CD4+Foxp3+)

Abstract

Context: CD4⁺ T lymphocytes are able to differentiate into distinct subtypes according to several immunological scenarios, including T helper (Th)1, Th2, Th17 and regulatory T (Treg) cells. CD4⁺ T cells are phenotypically flexible and have specific ion channels, such as the nicotinic acetylcholine receptors (nAChR) that could be modulated by peptides produced by marine snails, known as conotoxins. Their effect on T lymphocytes has not been explored and emerging evidence suggests that these peptides may have immunomodulatory activities.

Objective: This study investigated the effect of two Californiconus californicus-derived synthetic conotoxins on the proliferation and differentiation of T lymphocyte subpopulations Th1, Th2, Th17 and Treg.

Methods: Cells from lymph nodes of BALB/c mice were cultured in the presence of conotoxins cal14.1b and cal14.2c (5.5?μM), during 96?h. Cell proliferation and intracellular cytokine production (IFN-γ, IL-4, IL-17 and IL-10) were analyzed by flow cytometry.

Results and Discussion: cal14.1b and cal14.2c increased intracellular IL-10 production in Treg (CD3⁺CD4⁺Foxp3⁺) cells and decreased intracellular IL-17 production (CD3⁺CD4⁺) after 72?h of culture. Conotoxins did not show any effect on T cell proliferation nor Th1/Th2 balance.

Conclusion: These results suggest that synthetic conotoxins exert immunomodulatory activity, especially by regulating specific functions on T lymphocytes.     

IL-15 and IL-15Ralpha in CD4+T cell immunity

The cytokine IL-15 performs numerous functions, such as promotion of growth and survival, on a plethora of cell types from both the lymphoid and non-lymphoid compartments. Therefore, mice genetically engineered to either lack or overexpress functional IL-15 display reduced immunological responses and leukemia, respectively. Surprisingly, IL-15 protein is hardly found in serum or body fluids. Due to the lack of a clear demonstration of its presence as protein,IL-15 was often referred to as a "ghost cytokine ". Recently, however, membrane-bound IL-15 was detected in both a membrane-anchored form and an IL-15Ralpha -bound form on monocytes. Interestingly, the latter complex can ben transpresented to cells expressing the intermediate-affinity IL-2/15Rbeta-gamma C receptor and thereby support the survival and proliferation of T cells. Moreover, overlapping promoter elements indicate a model of co-regulation of IL-15 and IL-15Ralpha by which IL-15 activities are controlled in a cell-contact-dependent manner. In this review, recent reports on IL-15 are combined with previous observations and discussed in terms of their functional consequences for CD4+ T cell responses.     

Differential regulation of IL-13 and IL-4 production by human CD8+ and CD4+ Th0, Th1 and Th2 T cell clones and EBV-transformed B cells

In the present study, the requirements and characteristics forthe production of IL-13 by human T cells, T cell clones andB cells were determined and compared with those of IL-4. IL-13was produced by human CD4⁺ and CD8⁺ T lymphocyte subsets isolatedfrom peripheral blood mononuclear cells and by CD4⁺ and CD8⁺T cell clones. CD4⁺ T cell clones belonging to T_h0, T_h1-likeand T_h2-like subsets produced IL-13 following antigen-specificor polyclonal activation. In addition, EBV-transformed B celllines expressed IL-13 mRNA and produced small amounts of IL-13protein. Expression of IL-13 mRNA and production of IL-13 proteinby peripheral blood T cells and T cell clones was induced rapidlyand was relatively long lasting, whereas IL-4 production bythese cells was transient In addition, IL-13 mRNA expressionwas induced by modes of activation that failed to induce IL-4mRNA expression. IL-13 shares many biological activities withIL-4 which Is compatible with the notion that the IL-13 andIL-4 receptors share a common component required for signaltransduction. However, IL-13 lacks the T cell-activating propertiesof IL-4. Here we have shown that this is related to the factthat T cells fall to bind radiolabeled IL-13 and do not expressthe IL-13-speclflc receptor component Taken together, theseresults indicate that the differences In expression and biologicalactivities of IL-4 and IL-13 on T cells may have consequencesfor the relative roles of these cytokines In the immune response.     

Liposome-encapsulated antigens induce a protective CTL response against Listeria monocytogenes independent of CD4+ T cell help

Protection against intracellular pathogens is usually mediated by cytotoxic T lymphocytes (CTL). Induction of a protective CTL response for vaccination purposes has proven difficult because of the limited access of protein antigens or attenuated pathogens to the MHC class I presentation pathway. We show here that pH-sensitive PE/CHEMS liposomes can be used as a vehicle to efficiently deliver intact proteins for presentation by MHC class I. Mice immunized with listerial proteins encapsulated in such liposomes launched a strong CTL response and were protected against a subsequent challenge with L. monocytogenes . Remarkably, the CTL response was induced independently of detectable CD4⁺ T cell help.     

Lower proportion of CD19+IL-10+ and CD19+CD24+CD27+ but not CD1d+CD5+CD19+CD24+CD27+ IL-10+ B cells in children with autoimmune thyroid diseases

Abstract

Introduction: As it is generally known, regulatory B cells (Bregs) control inflammation and autoimmunity. The significance of Bregs in the population of children with autoimmune thyroid diseases (AITD) still offers plenty of potential to explore. The aim of this study was to estimate the expression of Bregs (phenotype CD19⁺CD24⁺CD27⁺IL-10⁺, CD19⁺IL-10⁺, CD1d⁺CD5⁺CD19⁺IL-10⁺ and CD1d⁺CD5⁺CD19⁺CD24⁺CD27⁺) in a paediatric cohort with AITD and in health controls.

Materials and methods: A total of 100 blood samples were obtained from 53 paediatric patients with Graves’ disease (GD) (N?=?12 newly diagnosed, mean age 12.5?±?3.5 and N?=?17 during methimazole therapy, mean age 12.7?±?4.4), Hashimoto’s thyroiditis (HT) (N?=?10 newly diagnosed, mean age 13.3?±?2.9 and N?=?10 during L-thyroxine therapy, mean age 13.7?±?3.4) and compared with healthy controls (C) (N?=?15, mean age 13.1?±?3.1). The expressions of the immune cell populations were analysed by four-color flow cytometry using a FASC Canto II cytometer (BD Biosciences).

Results: There was a decreasing tendency in the number of lymphocytes B producing IL-10 (B10) cells among all B lymphocytes and more widely, also among all lymphocytes, in each study group, as compared to C. We reported a reduction in IL-10 production in Bregs with the expression of CD19⁺CD24⁺CD27⁺IL-10 and CD1d⁺CD5⁺CD19⁺IL-10⁺ in both untreated and treated AITD.

Conclusions: Our data demonstrate that the reduction in the number of Bregs with CD19⁺CD24⁺CD27⁺IL-10⁺ and CD19⁺IL-10⁺ expression could be responsible for breaking immune tolerance and for AITD development in children.     

Immunoregulation of encephalitogenic MBP-NAc1-11-reactive T cells by CD4+ TCR-specific T cells involves IL-4, IL-10 and IFN-gamma

The generation of TCR transgenic (Tg) mice expressing a BV8S2 (Vbeta8 subfamily 2) chain specific for the encephalitogenic NAc1-11 region of MBP provides a unique system for evaluating the mechanisms involved in anti-TCR immunoregulation of EAE. In a previous study, we showed that vaccination with BV8S2 protein induced specific T cells that inhibited proliferation responses and encephalitogenic activity of MBP-reactive T cells in vitro, and resulted in a skewed production of Th2 cytokines by the MBP-reactive T cells. These data suggested that regulation of the encephalitogenic T cells was mediated by inhibitory cytokines rather than through a deletional mechanism. In the current study, we have employed the BV8S2 Tg mouse model to address the issue of which cytokines produced by anti-TCR-reactive T cells can regulate the function of encephalitogenic Th1 cells. Utilizing neutralizing anti-cytokine antibodies to reverse inhibitory effects of supernatants from BV8S2-specific T cells, we found that IL-4, IL-10, and to a lesser extent, IFN-gamma and TGF-beta, were the major regulatory cytokines responsible for inhibiting encephalitogenic activity, proliferation, and IFN-gamma secretion of MBP-NAc1-11-reactive Th1 cells. These results indicate that cytokine regulation is the major mechanism through which TCR specific CD4+ T cells regulate encephalitogenic and potentially other bystander Th1 cells.     

Prolonged skin allograft survival by IL-10 gene-introduced CD4 T cell administration

Both CD4 and CD8 T cells play crucial roles in immune responses in transplantation. Immunosuppressive drugs, such as FK506 and cyclosporin A, block the priming of alloreactive CD4 T(h) cells and the subsequent induction of allospecific CD8 cytotoxic effector T cells and inhibit allograft rejection. However, the desire to minimize chronic complications that may arise from the use of immunosuppressive agents drives the search for additional strategies for immunosuppression of allograft rejection. In this study, CD4 or CD8 T cells into which the IL-10 gene is introduced using an adenovirus vector containing human IL-10 (hIL-10) cDNA (Ad-hIL-10) and into mouse T cells transgenic for the Coxsackie virus and adenovirus receptor form a model system to study the effect of administration of IL-10-secreting T cells on the survival of the allogenic skin grafts. Ad-hIL-10-infected CD4 and CD8 T cells secreted a large amount of hIL-10 for 3-4 days in culture in vitro. Ad-hIL-10-infected CD4 T cells administered in vivo could be detected in the spleen for 7 days post-transfer. Significantly prolonged survival of grafts was observed in animals that received either Ad-hIL-10-infected activated CD4 T cells or T(h)2-skewed CD4 T cells as compared with controls. Furthermore, substantial enhancement of the effect was observed in B6.C-H2(bm1)/ByJ transplants. Thus, a direct manipulation of T cells through the introduction of the immunosuppressive cytokine gene IL-10 may be a novel strategy for the control of allograft rejection.