TH1/TH2 and TC1/TC2 profiles in peripheral blood and bronchoalveolar lavage fluid cells in pulmonary sarcoidosis

BACKGROUND: Sarcoidosis is thought to be a type-1 cytokine-mediated disorder. However, few data are available on the profiles of cytokine expression by TH cells at the single-cell level, as assessed by intracellular cytokine flow cytometry. Additionally, it remains to be determined whether the balance of TC1 and TC2 cells can be altered in sarcoidosis. OBJECTIVE: The aim of this study was to evaluate the TH1/TH2 and TC1/TC2 balances in sarcoidosis. METHODS: Using triple-color flow cytometry and phorbol 12-myristate acetate/ionomycin stimulation, we measured the production of the intracellular cytokines IFN-gamma and IL-4 in CD4+ and CD8+ T cells separately, which were obtained from peripheral blood and bronchoalveolar lavage fluid (BALF) of 20 patients with sarcoidosis, and compared their cytokine expressions with those of 10 normal subjects. RESULTS: Under unstimulated conditions, there were no significant differences in the proportion of cytokine-producing CD4+ or CD8+ T cells in peripheral blood or BALF between patients with sarcoidosis and normal control subjects. On stimulation with phorbol 12-myristate acetate/ionomycin for 4 hours, in BALF of the patients, but not in peripheral blood, we found a significant increase in the percentage of IFN-gamma-producing CD4+ T cells and a decrease in the percentage of IL-4-producing CD4+ T cells, resulting in a 3.5-fold higher ratio of IFN-gamma/IL-4-producing CD4+ T cells compared with that found in normal subjects. In contrast, no difference was found in the proportions of cytokine-producing CD8+ T cells or the ratio of IFN-gamma/IL-4-producing CD8+ T cells in either the peripheral blood or BALF between the patients and normal subjects. CONCLUSIONS: These findings suggest that the prominent shift toward a type-1 phenotype may occur in CD4+ T-cell populations but not in CD8+ T-cell populations in the affected organs of sarcoidosis.     

T cell responses to highly active antiretroviral therapy defined by chemokine receptors expression, cytokine production, T cell receptor repertoire and anti-HIV T-lymphocyte activity

The immunological correlates of highly active antiretroviral therapy (HAART)-induced suppression of human immunodeficiency virus type 1 (HIV-1) replication have been investigated. 20 HIV-1-infected patients with mean CD4+ T cell count of 298/microl, plasma viral load of 4.7 log10 copies/ml and naive for protease inhibitors (PI) were studied during12 months of HAART. An increased number of both CD4+ and CD8+ naive T cells and a normalization of the frequency of CCR5- and CXCR4-expressing CD4+ T cells were readily observed after starting therapy. Single cell analysis of cytokine production after 12 months of HAART showed an increased number of interleukin (IL)-2-, but not IL-4- and (IFN)-gamma-, producing T cells and a decreased percentage of CD8+ IFN-gamma + cells. A correlation between the frequency of IFN-gamma-producing T cells and that of memory, CCR5+ and CD95+ T cells was demonstrated in both CD4+ and CD8+ subsets. The diversity of T cell receptor (TCR) variable beta (BV) chain repertoire significantly increased after 12 months of HAART within the CD4+ but not the CD8+ T cell subset. However, the level of perturbation of the third complementarity-determining region (CDR3), was not significantly modified by effective therapy. The number of anti-HIV Gag and Pol cytotoxic T lymphocytes precursors (CTLp) decreased during HAART and highly correlated with the CD8 IFN-gamma response. Ameliorated clinical conditions were observed in all patients in absence of any opportunistic infections during all the study period. These observations indicate that a better restoration of immunity may be obtained in patients starting HAART at less advanced stages of the disease.     

CXCR3-mediated opposite effects of CXCL10 and CXCL4 on TH1 or TH2 cytokine production

BACKGROUND: Two variants of the CXCR3 receptor exist, one (CXCR3-A) reactive with CXCL9, CXCL10, and CXCL11 and the other (CXCR3-B) also reactive with CXCL4. Both variants are contemporarily expressed by human T cells. OBJECTIVE: We sought to investigate the in vitro effects of CXCL10 and CXCL4 on the production of TH1 or TH2 cytokines. METHODS: The cytokine profile of antigen-specific human CD4+ T-cell lines obtained in the absence or presence of CXCL10 or CXCL4 was evaluated by means of quantitative RT-PCR, flow cytometry, and ELISA. RESULTS: CXCL10 upregulated IFN-gamma and downregulated IL-4, IL-5, and IL-13 production, whereas CXCL4 downregulated IFN-gamma and upregulated TH2 cytokines. Similar effects were also observed on polyclonally activated pure naive CD4+ T cells. The opposite effects of CXCL10 and CXCL4 on TH1 and TH2 cytokine production were inhibited by an anti-CXCR3 antibody able to neutralize both CXCR3-A and CXCR3-B and were apparently related to the activation of distinct signal transduction pathways. Moreover, CXCL10 upregulated mRNA levels of T-box expressed in T cells and downregulated GATA-3 expression, whereas CXCL4 downregulated T-box expressed in T cells and upregulated GATA-3. Finally, CXCL4, but not CXCL10, induced direct activation of IL-5 and IL-13 promoters. CONCLUSION: CXCL10 and CXCL4 exert opposite effects on the production of human TH1 and TH2 cytokines, likely through their respective interaction with CXCR3-A or CXCR3-B and the consequent activation of different signal transduction pathways. This might represent an internal regulatory pathway of TH cell responses and might contribute to the modulation of chronic inflammatory reactions, including allergy.     

小儿慢性丙型肝炎外周血T细胞亚群和TH1/TH2型细胞因子的研究

目的通过研究小儿慢性丙型肝炎外周血T细胞亚群及TH1/TH2型细胞因子的表达,进一步探讨小儿慢性丙型肝炎的免疫发病机制。方法(1)流式细胞仪(FACS)检测16例慢性丙型肝炎患儿及10例正常对照外周血T细胞亚群。(2)将慢性丙型肝炎患儿和正常对照外周血单个核细胞(PBMC)体外培养72h后,用ELISA法检测培养上清中TH1型细胞因子(IFN-γ、IL-2、IL-12和TNF-γ)和TH2型细胞因子(IL-4、IL-10)的浓度。结果(1)CD4 细胞无明显变化。CD8 细胞与正常对照比较明显升高(P<0.05)。CD3 细胞升高,CD4 /CD8 比值下降,但与正常对照比较无统计学意义(P>0.05)。(2)PBMC培养上清中IFN-γ、IL-10和TNF-α的水平明显升高(P<0.01),而没有检测到IL-2、IL-4、IL-12的基础分泌。结论慢性丙型肝炎患儿体内T淋巴细胞存在数量和功能的异常,CD8 细胞数升高,CD4 细胞功能异常,表现在以TH2型细胞因子的分泌为主。这可能与丙肝病毒(HCV)感染的慢性化有关。     

Decreases in plasma TNF-alpha level and IFN-gamma mRNA level in peripheral blood mononuclear cells (PBMC) and an increase in IL-2 mRNA level in PBMC are associated with effective highly active antiretroviral therapy in HIV-infected patients

In this study, we investigated the cytokine profiles of 14 treatment-naive HIV-infected patients on the initiation of highly active antiretroviral therapy (HAART). At baseline, plasma levels of TNF-alpha and its mRNA in peripheral blood mononuclear cells (PBMC) were highest in the most severely immunocompromised patients (<200 CD4+ cells/mm3). After 12 months of HAART, the virus was undetectable in the plasma of all patients (<200 copies/ml), and median CD4 T cell counts had increased (+164 cells/mm3). We also observed a gradual decrease in the number of proviral DNA copies in PBMC and in immune activation, with lower levels of IFN-gamma mRNA in PBMC associated with weaker activation of CD8+ T cells and lower levels of plasma TNF-alpha. IL-2 mRNA levels in PBMC were found to increase in parallel. The decrease in TNF-alpha and IFN-gamma levels and the increase in IL-2 production appear to be correlated with the efficacy of HAART in naive immunocompromised HIV-infected individuals.     

Persistent central memory phenotype of circulating Fel d 1 peptide/DRB1*0101 tetramer-binding CD4+ T cells

BACKGROUND: Although substantial evidence suggests that T cells are important in the pathogenesis of atopic dermatitis (AD), little is known of the differentiation status of CD4+ T cells specific for common environmental allergens. OBJECTIVE: To determine the frequency, differentiation phenotype, and function of circulating allergen-specific CD4+ T cells in adult individuals with severe persistent AD and controls. METHODS: Using tetrameric complexes of an HLA DRB1*0101 restricted epitope from Fel d 1, the major IgE-reactive component of cat dander, we studied ex vivo and cultured T-cell frequency and phenotype in individuals with AD and healthy controls. Cytokine secretion was measured by ex vivo and cultured IFN-gamma, IL-4, and IL-10 enzyme linked immuno-spot analysis. RESULTS: Ex vivo Fel d 1-specific DRB1*0101-restricted CD4+ T cells express high levels of CCR7, CD62L, CD27, and CD28 and proportionately low levels of tissue-specific homing receptors and TH1 and TH2 cytokine production, placing the cells largely within the central memory subgroup. CONCLUSION: Circulating Fel d 1-specific DRB1*0101-restricted CD4+ T cells maintain central memory capacity, consistent with a potential to contribute to persisting clinical atopic disease. CLINICAL IMPLICATIONS: Persisting central memory characteristics of allergen-specific CD4+ T cells in individuals with AD may contribute to chronic disease.     

Effects of Ixodes scapularis and Borrelia burgdorferi on modulation of the host immune response: induction of a TH2 cytokine response in Lyme disease-susceptible (C3H/HeJ) mice but not in disease-resistant (BALB/c) mice.

Previous studies have demonstrated that both Ixodes scapularis saliva and Borrelia burgdorferi antigens modulated lymphokines and monokines in vitro. The studies presented here were designed to delineate the role of I. scapularis and B. burgdorferi in modulation of the host immune response in vivo. Infestation of C3H/HeJ mice with infected I. scapularis resulted in an up regulation of IL-4 as early as 8 days after tick infestation, while the levels of T helper cell type 1 (TH1) cytokines, interleukin-2 (IL-2) and gamma interferon (IFN-gamma), were significantly decreased by days 10 to 12. In contrast, the cytokine profile of BALB/c mice exposed to infected nymphal ticks resulted in only transient alterations in IL-4, IL-2, and IFN-gamma production throughout a 12-day period postinfestation. Although the IL-10 level was elevated in both C3H/HeJ and BALB/c mice infested with infected nymphal ticks, no significant difference in the levels of IL-10 was noted between the mouse strains. Flow-cytometric analysis demonstrated increases in the numbers of splenic B-cell and CD4+ lymphocytes in C3H/HeJ but not BALB/c mice exposed to infected ticks. Cell depletion experiments with C3H/HeJ mice demonstrated that CD4+ cells were the sole producers of IFN-gamma and IL-10 while both CD4+ and CD8+ splenocytes contributed to the production of IL-2 and IL-4. These findings suggest that B and CD4+ splenocytes are activated, increase in number, and produce a polarized TH2 response in C3H/HeJ mice exposed to infected I. scapularis. Given that C3H/HeJ mice are susceptible to Lyme disease and the initial TH2 polarization is not evident in BALB/c mice, effective control of this response may have ramifications for spirochete transmission in vivo.     

The quantitative and qualitative defect of CD4+ CD45RO+ memory-type T cells are involved in the abnormality of TH1 immunity in atopic dermatitis patients.

Peripheral blood mononuclear cells (PBMCs) obtained from atopic dermatitis (AD) patients produced low levels of IFN-gamma in response to Dermatophagoides farinae antigen (Der f Ag) plus IL-2 or OKT3 MoAb in contrast with PBMCs obtained from healthy donors. The reduced IFN-gamma production in AD patients' T cells appeared to be derived from the defect of CD4+ T cells but not CD8+ T cells. Indeed, from the cytoplasmic staining analysis of cytokines, it was demonstrated that the frequency of IFN-gamma producing CD4+ T cells (TH1 cells) in AD patients was markedly lower than that of healthy donors. From the phenotypic analysis using flow cytometry, it was also found that the number of CD4+ CD45RO+ memory type T cells was significantly reduced in AD patients compared with that of healthy donors. In addition to quantitative defect of memory type CD4+ T cells, functional defect of CD4+ CD45RO+ memory type T cells was also demonstrated in AD patients. Enriched CD4+ CD45RO+ T cells obtained from AD patients, who exhibited greatly reduced delayed-type hypersensitivity (DTH) response in tuberculin test, showed no significant TH1 immunity in terms of IFN-gamma production by stimulation with OKT3 MoAb or purified protein derivative (PPD). Thus, the immunological abnormality of TH1 immunity in AD patients appeared to be induced in concomitant with both the quantitative and qualitative defect of memory type CD4+ T cells.     

In vitro effector activity of Pneumocystis murina-specific T-cytotoxic-1 CD8+ T cells: role of granulocyte-macrophage colony-stimulating factor

Human immunodeficiency virus (HIV)-related opportunistic infections continue to occur in patients who are newly diagnosed with HIV infection, those in the early course of highly active antiretroviral therapy or nonadherent to HIV care, and other immunosuppressed individuals. One of the most common opportunistic infections in these patients is Pneumocystis pneumonia. CD8+ T cells are recruited to the lung after P. carinii infection and have been associated with both lung injury and host defense. This variability may be due to subpopulations of CD8+ T cells recruited to the lung. We have previously shown using adoptive transfer studies that in vivo-generated T-cytotoxic-1 (Tc1) CD8+ T cells, defined by the secretion of gamma interferon (IFN-gamma), have effector activity against Pneumocystis spp. in vitro as well as in vivo. To better understand the mechanisms of these effects, we generated, expanded, and tested Tc1 and Tc2 CD8+ T cells specific for P. murina ex vivo. Tc1-polarized CD8+ T cells secreted higher levels of IFN-gamma and granulocyte-macrophage colony-stimulating factor (GM-CSF) and lower levels of interleukin-4 (IL-4), IL-5, IL-10, and IL-13 than Tc2 CD8+ T cells when stimulated with P. murina antigen. Moreover, Tc1 CD8+ T cells demonstrated enhanced effector activity in a macrophage-mediated killing assay which was independent of cell contact. The augmentation in macrophage-mediated P. murina killing was significantly abrogated when GM-CSF was neutralized in the Tc1 CD8+ T cells. These data support the possibility that antigen-specific GM-CSF secretion is critical for effector activity of P. murina-specific Tc1 CD8+ T cells in vitro.     

Determination of cytokine co-expression in individual splenic CD4+ and CD8+ T cells from influenza virus-immune mice.

We have studied the patterns of interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma) co-expression displayed by individual splenic CD4+ and CD8+ T cells in response to influenza virus immunization. Unseparated spleen cells obtained from mice intraperitoneally (i.p.) injected with A/PR8 (H1N1) influenza virus (PR8) were cultured for 24 hr in the presence of ultraviolet-inactivated PR8. As controls, cultures of both naive spleen cells stimulated with PR8 or of immune cells lacking the inactivated virus were used. The frequencies of CD4+ and CD8+ T cells expressing IL-2, IL-4 and IFN-gamma were determined by three-colour flow cytometric analysis of fixed and saponin-permeabilized cells fluorescent-stained for either CD4 or CD8 surface molecules and for one of the following combinations of two intracellular cytokines: IL-2/IL-4, IL-2/IFN-gamma and IL-4/IFN-gamma. The results showed that immunization with influenza virus induces in both CD4+ and CD8+ T cells a heterogeneity of cytokine response patterns that do not follow the type 1/type 2 polarized response model, but with substantial differences between the two populations. In fact, the analysis of the phenotypes of virus-immune CD8+ T cells revealed similar significant proportions of cells either expressing any one of the three cytokines or co-expressing combinations of them (i.e. IL-4/IL-2, IL-4/IFN-gamma and IL-2/IFN-gamma), whereas immune CD4+ T cells were seen to express almost exclusively a single cytokine per cell. The observed patterns of cytokine production suggest that influenza virus immunization induces the expression of a type 0 cytokine pattern at both population and single cell levels in CD8+ T cells and exclusively at the population level in CD4+ T cells.     

Immunological changes in peripheral blood and in lymphoid tissue after treatment of HIV-infected subjects with highly active anti-retroviral therapy (HAART) or HAART + IL-2.

This study presents the immunophenotypic and functional analysis of lymphocyte subsets obtained from peripheral blood and lymphoid tissue from HIV+ individuals treated with highly active anti-retroviral therapy (HAART) alone or in combination with 6 million units international (MUI) s.c. IL-2. Before treatment, the HIV+ patients had reduced CD4 and increased CD8 values in the peripheral blood and lymphoid tissue and impaired cytokine production by peripheral blood mononuclear cells (PBMC). After 24 weeks of treatment, all the HIV+ patients demonstrated increased CD4 values in peripheral blood and lymphoid tissue. The use of IL-2 did not promote an additional CD4 expansion compared with HAART alone; increased 'naive' and CD26+ CD4 cells and reduced CD8 cells were found in the peripheral blood and lymphoid tissue of the IL-2-treated, but not of the HAART-treated patients. Both types of treatment induced a significant reduction of the CD8/CD38+ cells. While HAART alone had negligible effects on cytokine production by PBMC, the combined use of HAART + IL-2 was unable to increase the endogenous production of IL-2, but caused an increase of IL-4, IL-13 and interferon-gamma (IFN-gamma) and a reduction of monocyte chemoattractant protein-1 (MCP-1) production. These data suggest that, although in this schedule IL-2 has minimal efficacy on CD4 recovery when compared with HAART alone, it produces an increase of 'naive' and CD26+ CD4 cells and a partial restoration of cytokine production. These data may be used to better define clinical trials aiming to improve the IL-2-dependent immunological reconstitution of HIV-infected subjects.     

Normalization of immune activation in lymphoid tissue following highly active antiretroviral therapy

Although significant progress has been made in understanding immune reconstitution in peripheral blood following highly active antiretroviral therapy (HAART), less is known about immune changes in lymphoid tissue. Here, the expression of cytokine proteins (interferon gamma [IFN-gamma], interleukin [IL]-2, IL-4, IL-10, IL-1alpha, and IL-1beta) and surface antigens (CD4, CD8, CD1a, CD68) as well as cellular proviral HIV-1 DNA were determined in sequential tonsil biopsies before and at 4, 12, and 48 to 56 weeks posttherapy by quantitative in situ image analysis and fluorescent in situ 5;-nuclease assay (FISNA). Despite plasma virus suppression, a fraction of tonsil cells harbored pro-viral DNA for up to 1 year. A fourfold to eightfold increase in CD8+ T cells in tissue compared with seronegative controls and an increased frequency of CD1a+ dendritic cells prior to HAART reached control levels at week 56. The frequency of IFN-gamma expressing cells was 10-to 15-fold higher than controls before therapy and was comparable with findings in seronegative controls by week 56. Elevated baseline expression of IL-1alpha and IL-1beta was reduced by week 4 but IL-1alpha levels remained elevated in 1 of 3 patients at week 56. These findings suggest that with effective viral suppression the immune system in tissue may return to a more resting state.     

Intact T cell responses in ataxia telangiectasia

Ataxia telangiectasia (A-T) is an autosomal recessive multisystem disorder associated with a variable immune deficiency. The mechanism for this remains unclear. Qualitative and quantitative defects of cellular immunity have been previously reported. However, despite laboratory evidence of significant immune abnormalities, opportunistic infections are uncommon. To address this discrepancy, we analyzed cytokine production by quantitative real-time PCR and T cell function at the single cell level by flow cytometry in four A-T patients. CD4 and CD8 T cell subsets from these patients displayed intact signaling in response to anti-CD3 stimulation, similar to controls. Stimulated T cells from A-T patients also produced normal to increased levels of Th1 (IL-2, IFN-gamma) and Th2 (IL-10, IL-4) cytokines, relative to control values. Our results suggest that T cells from A-T patients may be more functionally intact than previously observed. This helps to explain the paucity of opportunistic infections encountered, unlike that encountered in other primary immunodeficiencies.     

Cytokine production by bronchoalveolar lavage T lymphocytes in chronic obstructive pulmonary disease

BACKGROUND: T lymphocytes (predominantly CD8+ cells) have previously been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). OBJECTIVE: We sought to describe the profile of cytokine production by CD8+ and CD4+ cells isolated from bronchoalveolar lavage fluid. METHODS: Bronchoalveolar lavage was performed in 11 patients with COPD (median FEV1, 63.3% of predicted value) and 9 healthy control subjects. CD8+ and CD4+ T cells were isolated by means of positive selection after macrophage depletion. CD8+ and CD4+ cells were activated with anti-CD3/CD28 antibodies for 60 hours before restimulation with phorbol 12-myristate 13-acetate-ionomycin and brefeldin. Three-color flow cytometry was used to simultaneously measure levels of intracellular cytokines. RESULTS: IL-4 was expressed by a higher percentage of stimulated CD8+ T cells (TC2) compared with CD4+ T cells (TH2) in patients with COPD (P = .01). In contrast, IFN-gamma was expressed in a significantly higher percentage of stimulated CD4+ T cells (TH1) than CD8+ T cells (TC1) in the COPD group (P = .04). TNF-alpha was expressed by almost all TC1 and TH1 cells, with virtually no expression by TC2 and TH2 cells. In addition, a small number of T cells expressing TNF-alpha alone without concomitant IFN-gamma or IL-4 expression were seen in the majority of subjects. There was a higher percentage of TC2 cells in subjects with COPD compared with that seen in the control group (P = .03). Stimulation with anti-CD3/CD28 antibodies increased the percentage of TC2 cells and decreased the percentage of TH2 cells. CONCLUSION: Our results suggest that there are increased numbers of TC2-like cytokine-expressing cells in the lungs of patients with COPD. CLINICAL IMPLICATIONS: These cells might be a source of TH2 cytokines, which might, at least in part, explain the lung eosinophilia associated with COPD exacerbations.     

Analysis of the in vitro cytokine production by liver-infiltrating T cells of patients with autoimmune hepatitis.

The pathogenic mechanisms underlying the development of autoimmune hepatitis (AIH) are still unclear. Since AIH is associated with the presence of various autoantibodies and certain HLA subtypes, it is likely that T and B cells play a major role in this disease. In this study we have determined the functional capacities of in vivo preactivated liver-infiltrating T cells (LTC) from patients with AIH. As controls we used LTC from patients with non-autoimmune hepatitis (non-AIH). Our results show that preactivated LTC from patients with AIH predominantly (190/255 clones) reside in the CD4+ population, whereas LTC in non-AIH are dominated by the CD8+ phenotype (148/254 clones). In view of this finding we have investigated the cytokine secretion patterns of 102 randomly chosen CD4+ T cell clones from six patients with AIH. As controls we have used 58 CD4+ LTC from 11 patients with non-AIH. All clones were stimulated by lectin and irradiated accessory cells and subsequent cytokine production was evaluated. LTC from patients with AIH have a lower interferon-gamma (IFN-gamma)/IL-4 ratio compared with LTC from non-AIH. Although clones from some patients with AIH produced very high amounts of IL-4 in vitro, this was not a constant finding. These results show that in vivo preactivated LTC from patients with AIH are mostly CD4+ T cells that produce more IL-4 than IFN-gamma. In contrast, LTC from patients with non-AIH are dominated by CD8+ and CD4+ T cells that produce significantly less IL-4 than IFN-gamma. Thus, liver-infiltrating T cells from patients with AIH and non-AIH belong to different functional T cell subsets. This may have implications for the regulation of humoral and cellular immune responses in inflammatory liver disease.     

Secretion of cytokines,histamine and leukotrienes in chronic urticaria

BACKGROUND: Approximately 35-40% of patients with chronic urticaria have an IgG autoantibody to the IgE receptor which can activate basophils and mast cells so that they release histamine. In this study we assessed the cytokine profile present in chronic urticaria sera, and then measured cytokine and leukotriene release from basophils and mast cells upon incubation with chronic urticaria sera. Finally we assessed cytokine expression at the single-cell level and characterized the T cell subpopulations involved in their production. We chose IL-4 as representative of Th2 lymphocytes and IFN-gamma for Th1 lymphocytes. METHODS: We analyzed IL-4, IL-5 and IFN-gamma in 60 chronic urticaria sera versus 51 controls. Sera were incubated with purified human basophils and cutaneous mast cells and the release of histamine, IL-4 and leukotrienes (C(4), D(4), E(4)) was quantitated. Immunoblotting was performed to identify IgG antibody to FcepsilonRIalpha, alpha subunit. We measured intracellular cytokine production in peripheral blood mononuclear cells of 17 chronic urticaria patients compared to 50 healthy controls. RESULTS: We found higher IL-4 levels (p = 0.028) in the sera of chronic urticaria patients (1.03 pg/ml) versus healthy donors (0.20 pg/ml) but no difference between urticaria sera and atopic control sera (0.52 pg/ml). We did not detect IFN-gamma or IL-5 in any serum. However, sera that activated basophils so that they released histamine also produced leukotriene and IL-4, and leukotriene production by cutaneous mast cells and basophils was closely correlated. However, there was no correlation between immunoblotting and the functional ability to induce either histamine or IL-4. After stimulating with PMA-ionomycin we found significant differences in CD4+ lymphocyte production of IL-4 and IFN-gamma with no differences in CD8+ lymphocyte production of either cytokine. CONCLUSION: Our data support the presence of basophil and mast cell activators in the sera of patients with chronic urticaria which can lead to the production of leukotrienes and IL-4 in addition to the histamine. IL-4 levels are similar to those seen in atopic subjects. We found that CD4+ T cells from patients with chronic urticaria are activated and tend to produce higher cytokine levels than CD4+ T cells from healthy controls. There were no differences when cytokine production by CD8+ lymphocytes was similarly assessed. These results are consistent with the histology found in biopsies of chronic urticaria lesions, where a CD4+-predominant infiltrate is found with cytokine production suggesting either a Th0 response or a mixture of Th1 and Th2 lymphocytes.