Th2 Cytokine Gene Expression Research Articles

Peanut lectin elicits a Th2 cytokine gene expression and protein secretion profile in mice

Peanut lectin elicits a Th2 cytokine gene expression and protein secretion profile in mice

The cell type-specific expression of the murine IL-13 gene is regulated by GATA-3.

IL-13, a Th2 cell-specific cytokine, is a major effector molecule mediating several pathological features of allergic asthma. However, the transcriptional regulation of the IL-13 gene remains unclear. Here we demonstrate, by using intracellular cytokine staining, that IL-13 is not always coexpressed with other Th2 cytokines in normal Th cells on a single cell basis. In addition, we identified and cloned a minimal inducible and cell type-specific promoter of the murine IL-13 gene. The cell type specificity of the minimal IL-13 promoter is mediated by a functionally critical GATA-3 site that binds endogenous GATA-3 proteins, whereas the induction by PMA/ionomycin is mediated by distinct cis-acting elements. Furthermore, by expressing GATA-3 in wild-type and c-maf transgenic Th1 cells, we demonstrate that the expression of IL-13 is regulated by a mechanism distinct from that regulating the expression of IL-4, and that the expression of Th1 and Th2 cytokine genes does not have to be mutually exclusive in effector Th cells.

Sequential monitoring of peripheral T-lymphocyte cytokine gene expression in the early post renal allograft period.

Despite numerous studies, the precise role of cytokines in acute renal allograft rejection remains unclear. In this study we have monitored sequential changes in peripheral T cell cytokine gene expression, correlating the changes with clinical events after adult renal transplantation, to provide a deeper insight of the role of cytokines in allograft rejection. Sequential changes in peripheral Th-1 [interleukin- (IL) 2 and interferon-gamma] and Th-2 (IL-4, IL-5, IL-10, and IL-13) cytokine gene expression in 43 patients with (n=15) and without (n=28) episodes of biopsy-proven rejection was monitored in the first 6 weeks after renal transplantation using a sensitive, semi-quantitative reverse-transcriptase polymerase chain reaction ELISA approach. Th-2 cytokines: IL-5 and IL13 expression increased before and during acute rejection, and decreased after successful antirejection therapy. A significant fall in IL-4 expression after transplantation and subsequent return to its baseline level of expression was observed in both nonrejectors and rejectors. IL-10 showed persistently high expression in nonrejectors, but in rejectors the expression fell during acute rejection, with a subsequent rise after antirejection therapy. Th-1 cytokines: IL-2 and IFN-gamma decreased in expression in the first week posttransplant in the rejectors, at the time of acute rejection (IL-2 only) and immediately after completion of antirejection therapy. Sequential monitoring of peripheral T cell cytokine gene expression after renal transplantation detected changes in expression that correlated with episodes of acute rejection and response to antirejection therapy. This approach may be applicable in the clinical laboratory for monitoring posttransplant changes in T cell alloreactivity and immunosuppression.

Developmentally regulated gene expression of Th2 cytokines in the brain

Given the critical role of cytokines in the regulation of an inflammatory response, we investigated whether certain cytokines are expressed in the brains of normal mice during maturation that could contribute to the immune-privileged nature of the CNS or potentially influence an immune-mediated illness such as experimental allergic encephalomyelitis. The gene expression of IFNγ (Th1 cytokine) and IL-4 (Th2 cytokine) was analyzed in the brain of several strains of mice. IFNγ was not detectable. However, IL-4 was present in the brains of neonatal mice, but not adult mice. Resident CNS cells are believed to be the source of the IL-4, because mice deficient in T cells (SCID and RAG2−/−) expressed the IL-4 gene in the CNS. Further analysis indicated that the gene expression of the Th2 cytokine transcription factor, GATA-3, correlated with IL-4 and IL-10 expression in the brain. Since GATA-3-deficient mice have an abnormal CNS, brain-derived Th2 cytokines may play an important role in CNS development, as well as potentially contribute to the immune-privileged nature of the brain.

Induction of experimental autoimmune encephalomyelitis in C57BL/6 mice deficient in either the chemokine macrophage inflammatory protein-1alpha or its CCR5 receptor.

Macrophage inflammatory protein (MIP)-1alpha is a chemokine that is associated with Th1 cytokine responses. Expression and antibody blocking studies have implicated MIP-1alpha in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). We examined the role of MIP-1alpha and its CCR5 receptor in the induction of EAE by immunizing C57BL / 6 mice deficient in either MIP-1alpha or CCR5 with myelin oligodendrocyte glycoprotein (MOG). We found that MIP-1alpha-deficient mice were fully susceptible to MOG-induced EAE. These knockout animals were indistinguishable from wild-type mice in Th1 cytokine gene expression, the kinetics and severity of disease, and infiltration of the central nervous system by lymphocytes, macrophages and granulocytes. RNase protection assays showed comparable accumulation of mRNA for the chemokines interferon-inducible protein-10, RANTES, macrophage chemoattractant protein-1, MIP-1beta, MIP-2, lymphotactin and T cell activation gene-3 during the course of the disease. CCR5-deficient mice were also susceptible to disease induction by MOG. The dispensability of MIP-1alpha and CCR5 for MOG-induced EAE in C57BL / 6 mice supports the idea that differential chemokine expression patterns represent differences in disease mechanism that underlie various models of EAE, and possibly distinct patterns of pathology seen in MS.

Enhanced T cell cytokine gene expression in mouse airway obliterative bronchiolitis.

Obliterative bronchiolitis (OB), chronic allograft rejection of the lung, is a major cause of morbidity and mortality after lung transplantation. Previous studies using the heterotopic mouse trachea model of chronic airway rejection have shown a T cell infiltrate composed of CD4+ and CD8+ T cells. The goal of these experiments was to characterize the pattern of T lymphocyte cytokines during chronic airway rejection using the heterotopic mouse trachea model. Isografts (BALB/c into BALB/c) and allografts (BALB/c into C57BL/6) were implanted into cyclosporin-treated animals and harvested 2, 4, 6, and 10 weeks posttransplant. Cytokine mRNA expression in these grafts was determined using reverse transcription polymerase chain reactions. Expression of Th1 cytokines, interleukin- (IL) 2 and gamma-interferon, and Th2 cytokines, IL-4, and IL-10 were analyzed, as well as the cytotoxic lymphocyte product granzyme B and expressed relative to beta-actin gene expression. In allografts, expression of IL-2 (P=0.002), gamma-interferon (P=2x10(-6)), granzyme B (P=0.003), IL-4 (P=0.06), and IL-10 (P=8x10(-6)) were 2- to 10-fold higher compared to isografts throughout the time-course of graft injury. Th1 and cytotoxic lymphocyte gene expression were increased to a greater extent than Th2 cytokines in allografts compared with isografts, and both Th1 and Th2 cytokine gene expression persisted at 6-10 weeks. These data suggest that Th1, Th2, and cytotoxic lymphocyte subtypes all contribute to the development of obliterative bronchiolitis in the heterotopic mouse trachea model. Efforts to reduce the development of obliterative bronchiolitis may require the antagonism of multiple T cell pathways.

Intrathymic Immunomodulation and the “Infectious” Tolerance Pathway in Allograft Recipients

Background.We have previously shown that >75% of LEW cardiac allografts survive indefinitely in BUF rats pretreated at Day −21 intrathymically (IT) with donor alloantigen in conjunction with a single intravenous dose of ALS. Spleen cells can adoptively transfer the tolerant state to new cohorts of test recipients. This study was designed to analyze cellular and humoral events contributing to the “infectious” tolerance pathway in this model.Methods.Spleen cells (25 × 106) harvested from BUF recipients bearing long-term cardiac allografts were injected intravenously into lightly irradiated (450 R) secondary BUF rats, followed 24 h later by transplantation of LEW of ACl hearts. Cardiac allografts were then analyzed serially by reverse transcription polymerase chain reaction for Th1 and Th2 cytokine gene expression. Donor-specific IgM and IgG alloantibody responses in host serum were screened by flow cytometry.Results.Transfer of regulatory spleen cells harvested between Days 80 and 140 from tolerant hosts induced tolerance to heart grafts in a donor-specific manner. In the early posttransplant period, selective sparing of Th2 cytokines was noted. Adoptively transferred hosts showed overall depression of IgM, but a vigorous IgG1 and IgG2a alloantibody response.Conclusion.IT + ALS-induced tolerance can be transferred in a donor-specific “infectious” manner to new cohorts of engrafted recipients. The development of tolerance is nontemporally bound, and associates with an early Th2-type immune deviation at the graft site. The elevated levels of T cell-dependent IgG1 and IgG2 may interfere with the antigen reactivity and alloresponsive effector functions, contributing to graft acceptance in the “infectious” tolerance pathway.

Spontaneous Autoimmune Thyroiditis in NOD.H-2h4 Mice

NOD.H-2h4 mice, which express I-Akon the NOD genetic background, spontaneously develop autoimmune thyroiditis (SAT) and anti-mouse thyroglobulin (MTg) autoantibodies. The incidence of SAT is nearly 100% in mice of both sexes 6–8 weeks after administration of 0.05% NaI in the drinking water. After reaching maximum severity, inflammation is chronic over the next 3–4 months. All mice that develop thyroid lesions also produce MTg-specific IgG1 and IgG2b autoantibodies. Thyroid lesions and anti-MTg autoantibodies did not develop in CBA/J (H-2k) or NOD.SWR(H-2q) mice after administration of NaI water. Both CD4+and CD8+T cells are involved in the initial development of SAT. Depletion of CD4+, but not CD8+, T cells after thyroid lesions have developed also markedly reduced SAT severity, indicating that CD4+T cells are required for both developing and maintaining SAT. Analysis of cytokine gene expression indicated that both Th1 and Th2 cytokines were expressed in thyroids of NOD.H-2h4 mice with SAT. Th1 and proinflammatory cytokines were maximally expressed 4–6 weeks after mice began receiving NaI water, while Th2 cytokine gene expression was greatest at 8–15 weeks, when lesions had reached maximal severity and were in the chronic phase. TGF-β was highly expressed in NOD.H-2h4 thyroids, irrespective of whether the mice had received NaI water or had thyroid lesions.

T-cell Expression of the Human GATA-3 Gene Is Regulated by a Non-lineage-specific Silencer

The GATA-3 transcription factor is required for development of the T-cell lineage and Th2 cytokine gene expression in CD4 T-cells. We have mapped the DNase-I-hypersensitive (HS) regions of the human GATA-3 gene in T-cells and non-T-cells and studied their transcriptional activities. HS I-III, located 5' from the transcriptional initiation site, were found in hematopoietic and non-hematopoietic cells, whereas HS IV-VII, located 3' from the transcriptional start site, were exclusively observed in T-cells. Among these hypersensitive sites, two transcriptional control elements were found, one in the first intron of the GATA-3 gene and the other between 8.3 and 5.9 kilobases 5' from the GATA-3 transcriptional initiation site. The first intron acted as a strong transcriptional activator in a position-dependent manner and with no cell-type specificity. The upstream regulatory element could confer T-cell specificity to the GATA-3 promoter activity, and analysis of this region revealed a 707-base pair silencer that drastically inhibited GATA-3 promoter activity in non-T-cells. Two CAGGTG E-boxes, located at the 5'- and 3'-ends of the silencer, were necessary for this silencer activity. The 3'-CAGGTG E-box could bind USF proteins, the ubiquitous repressor ZEB, or the basic helix-loop-helix proteins E2A and HEB, and we showed that a competition between ZEB and E2A/HEB proteins is involved in the silencer activity.

Multiple levels of regulation of Th2 cytokine gene expression.

Multiple levels of regulation of Th2 cytokine gene expression.

Cutting Edge: Differential Responsiveness of the IL-5 and IL-4 Genes to Transcription Factor GATA-3

AbstractThe cytokines IL-4 and IL-5 are often coordinately produced by Th2 cells as in asthma. However, it is unclear whether similar molecular mechanisms underlie transcription of the two genes. We have previously shown that the transcription factor GATA-3 is expressed in Th2 but not Th1 cells and is crucial for activation of the IL-5 promoter by different stimuli. In a different study, GATA-3 was shown to be sufficient for the expression of IL-4 and other Th2 cytokine genes. Here, we show that ectopic expression of GATA-3 is sufficient to drive IL-5 but not IL-4 gene expression. Also, in Th2 cells, antisense GATA-3 RNA inhibits IL-5 but not IL-4 promoter activation. The induction of IL-5 gene expression by GATA-3 involves high affinity binding of GATA-3 to an inverted GATA repeat in the IL-5 promoter.

An appraisal of T cell subsets and the potential for autoimmune injury

The initiation of T cell dependent immune responses requires the T cell to utilize a heterodimeric cell surface antigen receptor to recognize an antigenic peptide in association with major histocompatibility complex (MHC) molecules on the surface of antigen presenting cells (APCs). This is a necessary but insufficient signal for T cell activation. T cells must additionally receive a costimulatory signal that can be delivered through a variety of receptor-ligand pairs. Of these, the best characterized is the CD28-B7 (CD80 and CD86) couple. It has been appreciated for decades that the outcome of the T cell-APC interaction is highly variable and can lead to different forms of immune responses. The past decade has witnessed major advances in the definition of how distinct lymphocyte functions are dictated by expression of distinct cytokines, activation of defined signal transduction pathways, and, most recently, expression of distinct transcription factors. The production of ever increasing numbers of induced mutant mouse strains has created new reagents in which to analyze the role of particular cytokines or other proteins in defined immune responses. While the temptation remains to accomodate emerging information into reductionist models of T cell dependent immunopathology, it is our view that in vivo immune responses are highly complex and regulated events that defy simple categorization.

An update on the immunopathogenesis of asthma as an inflammatory disease enhanced by environmental pollutants.

The pathogenesis of asthma now centers on the role of bronchial mucosal inflammation of mixed cellularity in addition to the characteristic airways hyperresponsiveness and reversible obstruction. Mast cell mediators play an early role in the asthmatic airway response but through induced arachidonic acid metabolites and cytokine production may also participate in the late phase response. A unique feature of the late phase response is the abundant accumulation of eosinophils in the bronchial respiratory mucosa that is enabled by profound effects of the Th2 cytokine, IL-5. Additionally, the IL-4 gene cluster that is responsible for the levels of total serum IgE production has now been linked to asthma. With this new insight into the inflammatory mechanisms causing asthma, a mounting body of evidence exists to explain the recent increases in allergic disease prevalence resulting from environmental pollution. Air pollution, including the contribution by diesel exhaust particle emissions, has been shown to enhance both nasal IgE production and the gene expression of Th2 cytokines. It is believed that diesel particulates act as adjuvants in the immune system that promote the development of allergic inflammation.

B7-2 requirement for helminth-induced granuloma formation and CD4 type 2 T helper cell cytokine expression.

B7 ligands on APCs engage CD28/CTLA4 counter-receptors on T cells critical for T lymphocyte activation and functional differentiation of T helper subsets. To examine whether the ligands B7-1 (CD80) and B7-2 (CD86) affect gene expression of Th2 cytokines and development of Th2-mediated pathologic tissue reactions, mice were treated with anti-B7-1 or anti-B7-2 at the time of sensitization to footpad inoculation of Schistosoma mansoni eggs or induction of pulmonary granuloma by i.v. injected eggs. Anti-B7-2 treatment inhibited pulmonary granuloma formation by 74% and decreased levels of lung IL-5 and IL-13 transcripts compared with those in animals given control Ig by 20- and 5-fold, respectively, while anti-B7-1 administration has no effect. Anti-B7-2 treatment blocked CD4 cell gene expression of IL-4, IL-5, and IL-13, but had no effect on IFN-gamma or IL-10 in animals inoculated with S. mansoni ova, larvae from the filarial helminth Brugia malayi, or CFA. Anti-B7-1 administration had no effect on CD4 cell transcript levels of IL-4 and IL-5, but inhibited IFN-gamma in mice inoculated with ova. Similar effects of anti-B7-2 on CD4 cell cytokine expression were observed in IL-4 knockout mice, indicating the existence of an alternative pathway for induction and/or expression of these cytokine genes. These findings suggest a possible role for anti-B7-2 in the therapy of infectious and atopic diseases in which immunopathologic reactions are mediated by selected Th2 cytokines.

The Transcription Factor GATA-3 Is Necessary and Sufficient for Th2 Cytokine Gene Expression in CD4 T Cells

CD4 T cells potentiate the inflammatory or humoral immune response through the action of Th1 and Th2 cells, respectively. The molecular basis of the differentiation of these cells from naive T cell precursors is, however, unclear. We found that GATA-3 was selectively expressed in Th2 cells. GATA-3 is expressed at a high level in naive, freshly activated T cells and Th2 lineage cells, but subsides to a minimal level in Th1 lineage cells as naive cells commit to their Th subset. Antisense GATA-3 inhibited the expression of all Th2 cytokine genes in the Th2 clone D10. GATA-3 directly activated an IL-4 promoter-luciferase reporter gene in M12 cells. In transgenic mice, elevated GATA-3 in CD4 T cells caused Th2 cytokine gene expression in developing Th1 cells. Thus, GATA-3 is necessary and sufficient for Th2 cytokine gene expression.

ANALYSIS OF TH1/TH2 CYTOKINE GENE PROFILE DURING LOW DOSE IL-2 THERAPY IN PATIENTS WITH AIDS OR AIDS LYMPHOMA

Background: The progressive imbalance in T-cell cytokines is likely to contribute to the increased incidence of virally-associated malignancies during the course of HIV infection. Exogenous administration of TH1 cytokines may alter the progression of this imbalance. Here we use quantitative reverse transcription (RT)-PCR to analyze TH1(interferon-γ, IFN-γ) and TH2 (IL-10) cytokine gene expression in mononuclear cells(PBMC) obtained from AIDS and AIDS lymphoma patients receiving low dose IL-2 therapy. Changes in absolute number of CD4+ T cells, CD8+ T cell and CD3-CD56+ natural killer (NK) cells were also obtained. Methods: Blood samples were collected from eight patients (5 AIDS, 3 AIDS lymphoma) at regular intervals before, during and after the 90 day therapy of low dose IL-2 (1.0 × 106U/m2/day). Phenotyping was performed using a combination of directly conjugated monoclonal antibodies with flow cytometry. RNA obtained from fresh PBMC and subsets of PBMC were analyzed for changes in cytokine transcripts using quantitative RT PCR with a polycompetitor cDNA construct and the BioMax 1D densitometer Results: There was a significant increase in the absolute number of NK cells(mean percent increase 129 ± 26.3%, p ≤ 0.005). There were no consistent changes in CD4+ or CD8+ T cells. During IL-2 therapy there was a consistent increase in IFNγ gene expression in all 8 patients (mean percent increase 259 ± 77%, p≤ 0.005). In 4 patients IFN-γ gene expression decreased prior to the discontinuation of IL-2. In six of eight patients, IL-10 gene expression decreased during IL-2 therapy. Subset analysis in three cases indicated that IFN-γ gene expression was primarily within the NK cell subset. IL-10 expression was primarily in the monocytes. CD8+ T cells subsets had detectable IFN-γ and/or IL-10 gene expression in some instances. In 2 of 3 cases analyzed, monocyte IL-12 gene expression increased during IL-2 therapy. Conclusions: Our findings suggest that exogenous administration of low dose IL-2 to patients with AIDS or AIDS lymphoma can increase both the absolute number of NK cells and the endogenous IFN-γ gene expression in vivo. As NK cells provide requisite IFN-γ during the innate immune response to viral infection and IL-2-driven CD8+ T cells are critical for the antigen-specific immune response to viral infection, low dose IL-2 therapy may have a role in the prevention of virally-induced malignant transformation in patients with AIDS.

Th1/Th2 cytokine gene expression after mercuric chloride in susceptible and resistant rat strains.

Mercuric chloride (HgCl2) has contrasting effects on different rat strains: susceptible strains, e.g. Brown Norway (BN) develop polyclonal B cell activation, multiple autoantibodies and widespread tissue injury. Lewis (LEW) rats are resistant: no autoimmune response occurs after HgCl2; instead, there is immunosuppression. We have previously shown, by fully quantitative polymerase chain reaction (PCR), up-regulation of interleukin-4 (IL-4) gene expression in HgCl2-treated BN rats, implicating Th2 cells in the autoimmune syndrome. Involvement of the reciprocal Th1 subset, producing interferon-gamma (IFN-gamma), in resistance of LEW rats to HgCl2 has been suggested. We now report extensive analysis of Th1 and Th2 cytokine gene expression in spleen and lymph nodes of susceptible (BN) and resistant (LEW) rats after HgCl2. IL-4 and IFN-gamma were analyzed by quantitative PCR, other cytokines were assessed using semiquantitative PCR: the relative merits of these two techniques are discussed. We show pronounced up-regulation of IL-4 and more modest up-regulation of IFN-gamma in BN rats, but no up-regulation of either in LEW rats. Baseline levels of IFN-gamma were higher in Lew rats. Semiquantitative PCR showed increased expression of IL-2, IL-6 and IL-10 in BN; in LEW rats only IL-10 was increased. There was no marked change in IL-5, IL-13 or transforming growth factor-beta (TGF-beta) in either strain. These data further support the key role of IL-4 in HgCl2-induced autoimmunity, and suggest that failure of up-regulation of IL-4, together with higher baseline IFN-gamma expression, accounts for resistance of LEW rats to HgCl2. However, neither IFN-gamma nor TGF-beta can be implicated in HgCl2-induced immunosuppression in the LEW rat in vivo: our data suggest a role for IL-10 in this phenomenon.

Human lung mast cell IL-5 gene and protein expression: temporal analysis of upregulation following IgE-mediated activation.

The late-phase of allergic asthma is characterized by infiltration of the airway with eosinophils within 6 h of mast cell activation. Pro-eosinophilic/pro-allergic (TH2) cytokines, originally described as T-lymphocyte products, have recently been ascribed to mast cells as well. To date, however, it is unknown if TH2 cytokine gene expression by the human mast cells is subject to receptor-mediated regulation analogous to that of T-cells, and if messenger RNA (mRNA) expression results in protein secretion occurring in a temporal context consistent with the late-phase response. We examined interleukin-4 (IL-4), IL-5, and IL-6 mRNA expression induced by anti-IgE activation of human lung explants as assessed using reverse transcription/polymerase chain reaction (RT-PCR). Anti-IgE stimulation resulted in rapid and sustained upregulation of IL-5 message, but did not have analogous effects on IL-4 or IL-6. Using quantitative-competitive PCR, we demonstrated that 100 ng of total cellular RNA from human lung contained 1 fg of IL-5 mRNA; this increased to 100 fg 4 h after anti-IgE activation. The source of the anti-IgE-enhanced IL-5 mRNA is likely the mast cell itself, as anti-CD3 activation of lung led to a dissimilar array of cytokine expression. In addition, human lung mast cells purified to near homogeneity expressed IL-5 mRNA after activation, as shown by both RT-PCR and in situ hybridization. In both lung fragments and purified human lung mast cells, the modulation of IL-5 mRNA expression preceded the secretion of IL-5 protein, detected as early as 4 h after activation. Neither isolated purified mast cells nor purified peripheral blood T cells could be induced to secrete detectable amounts of IL-5 protein when activated only with antibodies against IgE or CD3-T cell receptor complex, respectively. However, mast cells (n = 4) and T cells (n = 6) cultured at comparable concentrations (4 x 10(6)/ml) activated through their respective antigen receptors in the presence of phorbol ester yielded comparable IL-5 production (253 +/- 126 pg/ml versus 183 +/- 75 pg/ml, mean +/- SE). We conclude that mast cells are analogous to T cells in the requirement of co-stimuli for the production of IL-5 protein. Moreover, the rapid kinetics of IgE-mediated IL-5 transcription and protein elaboration are consistent with a primary role for mast cell activation directly leading to late-phase airway eosinophilia.

Donor specific bone marrow cells suppress lymphocyte reactivity to donor antigens and differentially modulate TH1 and TH2 cytokine gene expression in the responder cell population

Previous studies have shown that post-transplantation infusion of donor specific bone marrow following a non-specific potent immunosuppressive agent such as antilymphocyte globulin (ALG) can significantly enhance graft survival compared to ALG alone. This enhancement remains variable and is thought to occur through the induction of specific partial tolerance to the renal allograft, but the underlying cellular mechanisms have not been clearly identified. In order to improve the efficacy of this specific immunosuppressive treatment and to study the events leading to enhanced allograft survival, we sought to establish a simple in vitro model based on a mixed lymphocyte reaction (MLR). we show that cellular poliferation seen in a normal MLR can be suppressed by addition of donor specific bone marrow cells (BMC). Significantly, this suppression is not observed with either third party BMC or donor specific peripheral blood mononuclear cells (PBMC). We have defined the optimum conditions of bone marrow infusion regarding number of BMC, their handling and culture, and simple enrichment procedures. Using a semiquantitative polymerase chain reaction assay, we have studied the cytokine gene expression in MLR modulated by donor specific BMC. In an unmodified allogeneic response, the responder cells show increased expressed of interleukin-2 (IL-2) gamma-interferon IFN-γ and receptor (IL2R) mRNA, and no IL-10 mRNA. When responder cells are cultured with BMC of the stimulator, there is a 256-fold decrease in IL2 mRNA, and a 64-fold decrease in IFN-γ and IL-24 mRNA. There is also a 64-fold increase in IL-10 mRNA. This effect is even more marked when the BMC are depleted of CD3 + cells. The kinetics of addition of donor specific BMC to the normal allogeneic MLR culture and specificity of the action of BMC are also elucidated. Our data suggest that the enhancement of graft survival observed with donor BMC may operate through decreased proliferation of reactive T cell clones (due to decreased IL-2/IL-2R) and suppressed monocyte functions (due to decreased IFN-γ and increased IL-10 gene expression).

Requirement of CTLA-4 counter receptors for IL-4 but not IL-10 elevations during a primary systemic in vivo immune response.

The CD28/CTLA-4 costimulatory signal is required for TCR-mediated T cell activation resulting in increased IL-2 production in vitro, but its role in IL-4 production is unclear and few studies have examined the function of CTLA-4/CD28 in the in vivo immune response. We have examined the in vivo effects of blocking the interaction of B7 with its ligands, CTLA-4 and CD28, in an IL-4 dominant in vivo immune response to goat anti-mouse IgD. This response is characterized by elevations in serum Igs preceded by elevations in IL-2 and the Th2 cytokines: IL-4, IL-9, and IL-10. The fusion protein CTLA4-Ig administered during the in vivo immune response to goat anti-mouse IgD caused an inhibition in elevations of IL-2, IL-4, and IL-9 gene expression at both day 3 and day 6 after immunization. In contrast, IL-10 cytokine gene expression as late as day 6 after immunization was not decreased. Cell sorting analysis demonstrated that TCR-alpha beta +, CD4+ T cells were the primary source of the elevated IL-10, suggesting that T cell activation leading to IL-10 gene expression may not require CTLA-4 ligand interactions. Similarly CTLA4-Ig completely blocked elevations in the number of IL-4- but not IL-10-secreting cells, as measured by ELISPOT, in both unsorted splenic cells and sorted CD4+, TCR-alpha beta+ T cells. In situ staining of spleen sections also showed inhibition of IL-4-producing cells. These results suggest that, with the notable exception of IL-10, interaction, of B7 with its ligands is required for elevated Th2 cytokine gene expression and secretion during a primary systemic IL-4-dominant response.