Identification of serum IFN-α and IL-33 as novel biomarkers for type 1 autoimmune pancreatitis and IgG4-related disease.

IgG4-related disease (IgG4-RD) is a multi-organ autoimmune disease characterized by elevated serum IgG4 concentration. Although serum IgG4 concentration is widely used as a biomarker for IgG4-RD and type 1 autoimmune pancreatitis (AIP), a pancreatic manifestation of IgG4-RD, a significant number of patients have normal serum IgG4 levels, even in the active phase of the disease. Recently, we reported that the development of experimental AIP and human type 1 AIP is associated with increased expression of IFN-α and IL-33 in the pancreas. In this study, we assessed the utility of serum IFN-α and IL-33 levels as biomarkers for type 1 AIP and IgG4-RD. Serum IFN-α and IL-33 concentrations in patients who met the diagnostic criteria for definite type 1 AIP and/or IgG4-RD were significantly higher than in those with chronic pancreatitis or in healthy controls. Strong correlations between serum IFN-α, IL-33, and IgG4 concentrations were observed. Diagnostic performance of serum IFN-α and IL-33 concentrations as markers of type 1 AIP and/or IgG4-RD was comparable to that of serum IgG4 concentration, as calculated by the receiver operating characteristic curve analysis. Induction of remission by prednisolone treatment markedly decreased the serum concentration of these cytokines. We conclude that serum IFN-α and IL-33 concentrations can be useful as biomarkers for type 1 AIP and IgG4-RD.

Hypogammaglobulinemia in children after allogeneic hematopoietic stem cell transplantation: a cytokine mediated immunoglobulin isotype class switch arrest?

BACKGROUND: Hypogammaglobulinemia (hypo-IgG) is common early post-HSCT in children, occasionally necessitating long-term immunoglobulin (Ig) G replacement therapy. IgG replacement may not reduce mortality, although infectious complications are decreased PROCEDURE: Clinical data and samples from 86 children were analyzed retrospectively with the aim to identify risk factors for developing long-term hypo-IgG (i.e., requiring ≥ 3 months IgG replacement) post-HSCT and studying the underlying biology. Laboratory studies covered serum cytokines, IGHG2 genotyping and routine laboratory investigations. Results were analyzed statistically. RESULTS: Forty-eight percent of the children developed long-term hypo-IgG. These children were younger (<5 years) and had higher acute GvHD incidence, but had better overall survival (88% vs. 69%, P = 0.036). Significantly lower Ig levels post-HSCT but equal immune cell recovery were seen in patients with long-term hypo-IgG compared with those of transient or no hypo-IgG. Pre-HSCT IL-6 and -7 and post-HSCT BAFF and APRIL levels were significantly higher in the long-term hypo-IgG group. CONCLUSIONS: Findings suggests an unfavorable cytokine milieu for graft-derived immune recovery, possibly inducing Ig isotype class switch arrest. Younger age, acute GvHD, and higher pre-HSCT IL-6 levels were identified as significant risk factors for long-term hypo-IgG. Long-term hypo-IgG post-HSCT does not need to be unfavorable and could be an effect of deteriorated cytokine signaling.

Low-dose rituximab therapy for refractory thrombocytopenia in patients with systemic lupus erythematosus--a prospective pilot study.

OBJECTIVES: To evaluate the safety and efficacy of low-dose rituximab therapy for refractory thrombocytopenia in patients with SLE. METHODS: Ten adult SLE patients with severe refractory thrombocytopenia (mean platelet count 10.4 × 10(9)/l) were enrolled in this prospective pilot study. All patients had failed traditional high-dose CSs and immunosuppressants including methylprednisolone pulse therapy. Patients were scheduled to receive i.v. rituximab at a dose of 100 mg once weekly for 4 weeks. Previous dose of CSs were gradually tapered, and immunosuppressants were withdrawn. Patients were followed at Weeks 4, 12, 24 and 36. RESULTS: All patients completed four courses of low-dose rituximab infusion. At Week 4, two (20%) patients achieved complete responses (CRs, platelet count >100 × 10(9)/l). The CR rate increased to 60% (six patients) at Week 12, was maintained at Week 24 and began to drop at Week 36 (four patients, 40%). Overall response (OR, platelet count >50 × 10(9)/l) was achieved in 5/10, 6/10, 7/10 and 5/10 patients at Weeks 4, 12, 24 and 36, respectively. Peripheral CD19(+) B cells were depleted (<5 × 10(6)/l) in all patients at Week 4, and gradually increased at Weeks 24 and 36. Serum C3, IgG, IgA and IgM levels did not change significantly (P < 0.05). Infusion reaction was observed in two patients. One patient developed pulmonary thrombosis at Week 14 and active tuberculosis at Week 25. CONCLUSIONS: Low-dose rituximab therapy is effective in treating severe thrombocytopenia in SLE patients who do not respond to vigorous glucocorticoid plus immunosuppressants, and in most cases is safe.

Effects on mouse immunity of long-term exposure in vivo to minute amounts of HEMA.

2-Hydroxyethyl methacrylate (HEMA) leaks from cured restorations over time. Hence, HEMA can come into contact with cells of the immune system that are present in the oral mucosa and in the dental pulp. In this study, our aim was to develop a model of long-term exposure to minute amounts of HEMA and to record the immunological effects in mice. Osmotic pumps filled with either HEMA (8.2 M or 183 µM) or 0.9% NaCl (control) were implanted subcutaneously into the backs of mice and left in situ for 40 d, during which time the animals were immunized with ovalbumin (OVA). After 40 d, spleens and serum were collected. Splenocyte proliferation in vitro was analyzed by measuring the decomposition of [(3)H]thymidine. Splenocyte cytokine production and serum anti-OVA IgG, IgM and IgA activity were analyzed using ELISAs. Mice exposed to both the higher and the lower HEMA concentrations gained significantly less weight and produced significantly reduced amounts of interleukin-2 (IL-2) in vitro compared with control mice. Mice exposed to the lower HEMA concentration had a significantly reduced concanavalin A-stimulated splenocyte proliferation in vitro and blood anti-OVA IgA activity. In conclusion, long-term exposure to minute amounts of HEMA in vivo affects the general health of mice and suppresses certain immunological functions.

A pilot study on the changes in immunity after ACTH therapy in patients with West syndrome.

Adrenocorticotropic hormone (ACTH) has been the first-line drug for the treatment of West syndrome, although the therapy has various adverse effects. ACTH depresses resistance to a variety of bacterial, viral, protozoal, and fungal agents. The timing of the various vaccinations is delayed after ACTH therapy in Japan, because the immune system is believed to be affected for approximately 6 months. However, the duration of the effect of ACTH on the immune system is not known. Therefore, we examined changes in the immunity levels before and after ACTH therapy. We measured white blood cell counts, lymphocyte counts, T/B cell counts, CD4(+) and CD8(+) T cell counts, CD 4/8 ratio, lymphocyte blastoid transformation by PHA or Con-A, and the levels of IgA, IgM, and IgG before, immediately after, and 1, 3, 6, and 12 months after ACTH therapy. The lymphocyte counts and CD4(+) T cell counts were significantly decreased immediately after and at 1 and 3 months after the therapy, and did not return to the previous levels even at 6 months and 12 months after ACTH treatment; however, these levels returned to within normal limits (within the 95% confidence interval). Immunoglobulin levels did not change after the ACTH therapy. Helper T cells were more depressed than cytotoxic T cells after ACTH therapy.

Human serum antibody reactivity towards Paracoccidioides brasiliensis antigens treated with sodium metaperiodate.

In this study, we evaluated the profile of anti-Paracoccidioides brasiliensis immunoglobulin isotypes in serum from patients with the acute and chronic forms of paracoccidioidomycosis, using the whole Paracoccidioides brasiliensis antigen and the antigen treated with sodium metaperiodate. All the immunoglobulin isotypes present in the serum from patients with the acute and chronic forms of paracoccidioidomycosis presented higher reactivity towards the whole antigen than to the antigen treated with metaperiodate (P < 0.05). The reactivity of IgG and IgM to the antigen treated with metaperiodate was greater in serum from patients with the acute form of the disease (P < 0.05), while IgA was more reactive in serum from patients with the chronic form (P < 0.05). There was greater reactivity of IgG1 and IgG2 to the whole antigen and the antigen treated with metaperiodate in the serum from patients with paracoccidioidomycosis than there was in serum from patients with other parasitic infections (P < 0.05). Furthermore, IgG1 from patients with the acute form recognized the 19kDa, 27kDa and 31kDa antigens in the western blot test. Thus, the results suggest that modifications to the epitopes of Paracoccidioides brasiliensis antigens may help to improve the immunodiagnosis of paracoccidioidomycosis.

Human serum antibody reactivity towards Paracoccidioides brasiliensis antigens treated with sodium metaperiodate / Reatividade de anticorpos de soros humanos a antígenos de Paracoccidioides brasiliensis tratados com metaperiodato sódico

In this study, we evaluated the profile of anti-Paracoccidioides brasiliensis immunoglobulin isotypes in serum from patients with the acute and chronic forms of paracoccidioidomycosis, using the whole Paracoccidioides brasiliensis antigen and the antigen treated with sodium metaperiodate. All the immunoglobulin isotypes present in the serum from patients with the acute and chronic forms of paracoccidioidomycosis presented higher reactivity towards the whole antigen than to the antigen treated with metaperiodate (P < 0.05). The reactivity of IgG and IgM to the antigen treated with metaperiodate was greater in serum from patients with the acute form of the disease (P < 0.05), while IgA was more reactive in serum from patients with the chronic form (P < 0.05). There was greater reactivity of IgG1 and IgG2 to the whole antigen and the antigen treated with metaperiodate in the serum from patients with paracoccidioidomycosis than there was in serum from patients with other parasitic infections (P < 0.05). Furthermore, IgG1 from patients with the acute form recognized the 19kDa, 27kDa and 31kDa antigens in the western blot test. Thus, the results suggest that modifications to the epitopes of Paracoccidioides brasiliensis antigens may help to improve the immunodiagnosis of paracoccidioidomycosis.

Neste trabalho, foi avaliado o perfil de isotipos de imunoglobulinas anti-Paracoccidioides brasiliensis em soros de pacientes com formas crônica e aguda de paracoccidiodomicoses usando antígeno total e tratado com meta-periodato. Todos os tipos de imunoglobulinas presentes nos soros de pacientes com formas aguda e crônica apresentaram alta reatividade ao antígeno total quando comparado ao tratado com meta-periodato (P < 0,05). Houve maior reatividade de IgG e IgM anti-antígeno tratado com meta-periodato em soros de pacientes com forma aguda da doença (P < 0,05), enquanto IgA foi mais reativa em soros da forma crônica (P < 0,05). Houve maior reatividade de IgG1 e IgG2 com antígeno total e tratado com meta-periodato em soros de pacientes comparados aos com outras parasitoses (P < 0,05). Além disso, IgG1 de pacientes com a forma aguda reconhecem antígenos de 19kDa, 27kDa e 31kDa por western blot. Assim, os resultados sugerem que alterações nos epitopos de antígenos de Paracoccidioides brasiliensis podem auxiliar no aprimoramento do imunodiagnóstico da paracoccidioidomicose.

Immunotoxicity of aflatoxin B1: impairment of the cell-mediated response to vaccine antigen and modulation of cytokine expression.

Aflatoxin B1 (AFB1), a mycotoxin produced by Aspergillus flavus or A. parasiticus, is a frequent contaminant of food and feed. This toxin is hepatotoxic and immunotoxic. The present study analyzed in pigs the influence of AFB1 on humoral and cellular responses, and investigated whether the immunomodulation observed is produced through interference with cytokine expression. For 28 days, pigs were fed a control diet or a diet contaminated with 385, 867 or 1807 microg pure AFB1/kg feed. At days 4 and 15, pigs were vaccinated with ovalbumin. AFB1 exposure, confirmed by an observed dose-response in blood aflatoxin-albumin adduct, had no major effect on humoral immunity as measured by plasma concentrations of total IgA, IgG and IgM and of anti-ovalbumin IgG. Toxin exposure did not impair the mitogenic response of lymphocytes but delayed and decreased their specific proliferation in response to the vaccine antigen, suggesting impaired lymphocyte activation in pigs exposed to AFB1. The expression level of pro-inflammatory (TNF-alpha, IL-1beta, IL-6, IFN-gamma) and regulatory (IL-10) cytokines was assessed by real-time PCR in spleen. A significant up-regulation of all 5 cytokines was observed in spleen from pigs exposed to the highest dose of AFB1. In pigs exposed to the medium dose, IL-6 expression was increased and a trend towards increased IFN-gamma and IL-10 was observed. In addition we demonstrate that IL-6 impaired in vitro the antigenic- but not the mitogenic-induced proliferation of lymphocytes from control pigs vaccinated with ovalbumin. These results indicate that AFB1 dietary exposure decreases cell-mediated immunity while inducing an inflammatory response. These impairments in the immune response could participate in failure of vaccination protocols and increased susceptibility to infections described in pigs exposed to AFB1.

Changes in immunoglobulin isotypes and immunoglobulin G (IgG) subclasses during highly active antiretroviral therapy: anti-p24 IgG1 closely parallels the biphasic decline in plasma viremia.

SUMMARY: The effects of highly active antiretroviral therapy (HAART) on immunoglobulin isotypes and immunoglobulin G (IgG) subclasses were studied in 12 patients in early stages of HIV-1 infection. Blood samples were obtained at enrollment and 2, 4, 8, 12, 24, 48, and 120 weeks after initiation of HAART. Immunoglobulin concentrations were determined by nephelometry, and anti-p24-specific IgG and IgG1 levels were determined by an enzyme immunoassay. Overall time changes were analyzed in analysis of variance models. IgG and IgG1 levels showed a marked overall decline, whereas other immunoglobulin isotypes and IgG subclasses did not change significantly. Anti-p24-specific IgG1 levels decreased considerably and significantly more in virus isolation-negative patients than in virus isolation-positive patients, as defined according to the ability to isolate HIV-1 from their CD4+ T cells after initiation of therapy. Anti-p24 IgG levels showed a similar but overall weaker decline in the two groups. However, the anti-p24 IgG1 level followed the biphasic decline in plasma viremia more closely than the anti-p24 IgG level, with an initial sharp decline that leveled off with time. These findings suggest that the main reduction in immunoglobulin levels is caused by reduced HIV-1-specific antigen stimulation rather than a general reduction in immune activation. Using anti-p24 IgG1 as a parameter of response to the effect of HAART merits further investigation.

Antiphospholipid antibodies in young women with and without oral contraceptive use.

The role of thrombophilia in the elevated risk of thromboembolism during oral contraceptive use has been established. We performed a cross-sectional study among young women to survey the occurrence of antiphospholipid antibodies among users and non-users of oral contraceptives. Serum levels of immunoglobulin (Ig)G, IgA and IgM isotypes of anti-beta2-glycoprotein I and anticardiolipin antibodies were measured by validated enzyme-linked immunosorbent assay methods. Combining all types of antiphospholipid antibodies, pill-users had an elevated antibody titre more than twice as frequently as non-users (odds ratio, 2.3; 95% confidence interval, 1.1-5.1). The higher frequency of elevated antibody titre was related most commonly to IgG type anti-beta2-glycoprotein I antibodies. Oral contraceptive use increases the risk of elevated antiphospholipid antibody levels among asymptomatic young women.

Disruption of the homeobox gene Hoxb-6 in mice results in increased numbers of early erythrocyte progenitors.

Hox genes encode transcription factors that are required for proper development of certain tissues and for patterning of the hindbrain, the limbs, and skeleton. They are also expressed in the hematopoietic system with a preference for specific cell lineages. To determine the role of Hoxb-6 in normal hematopoiesis, mice with a targeted disruption in the Hoxb-6 gene were generated. Mature hematopoietic cell types and immune responses are normal in homozygous Hoxb-6 mutants. Clonogenic progenitor cell assays demonstrate an increased number of early erythroid progenitor cells in the bone marrow and fetal liver of mutants, while differentiation of other cell lineages is unaffected. These results suggest that Hoxb-6 controls the generation, proliferation, or survival of erythroid progenitor cells.

The regulatory effects of all-trans-retinoic acid on isotype switching: retinoic acid induces IgA switch rearrangement in cooperation with IL-5 and inhibits IgG1 switching.

All-trans-retinoic acid (RA) can induce germline Calpha transcription in LPS-stimulated murine mu(+)B-cells by a TGF-beta-independent mechanism. In the present study, we examined whether RA can further drive the IgA switching process to Smu-Salpha switch rearrangement by DC-PCR. RA alone could not induce switch rearrangement but required the cooperation of IL-5. RA has another effect on isotype switching; RA strongly inhibits IL-4-dependent IgG1 and IgE production. To analyze the mechanism of IgG1 inhibition, we tested whether RA can inhibit IL-4-dependent Smu-Sgamma1 switch rearrangement. IL-4 by itself could induce Smu-Sgamma1 switch rearrangement in LPS-stimulated mu(+)B-cells. Addition of RA inhibited this reaction. RA also showed an inhibitory effect on the preceding step, i.e., Igamma1Cgamma1 transcription. Therefore, RA inhibition of Smu-Sgamma1 switch rearrangement was regulated at the level of germline Cgamma1 transcription. We further analyzed the amounts of both Igamma1Cgamma1 and IalphaCalpha expressed in LPS-stimulated B-cells exposed to mixtures of the two switch inducers, RA and IL-4, at various concentrations and found that the two transcripts were regulated antagonistically. These results indicated that RA can regulate isotype switching at the level of germline transcription and directs switching to IgA with the help of IL-5 and inhibits IgG1 switching.

Intravenous immunoglobulin inhibits IgE production in human B lymphocytes.

BACKGROUND: Intravenous immunoglobulin (IVIG) is commonly used as both an immune-enhancing and immune-modulating agent. Treatment with high doses of IVIG diminishes IgE secretion in patients with severe steroid-dependent asthma. OBJECTIVE: We studied the action of IVIG on IgE production in highly purified B lymphocytes stimulated without additional T cells to determine the action of IVIG on B lymphocytes. METHODS: Human B cells were purified from tonsils, and T lymphocytes were removed by E-rosetting. B cells were cultured with IL-4 (400 U/mL) and anti-CD40 antibodies (1 microg/mL¿, with or without additional IVIG. Cell proliferation was determined by 3[H]-thymidine uptake, and supernatant IgE was determined by ELISA. Cell cycle analysis was performed by flow cytometry, and IgE transcripts were measured by in situ hybridization. RESULTS: IVIG (5 mg/mL) decreased B-cell proliferation in IL4/anti-CD40-stimulated B cells by an average of 74% (+/-6%). Addition of IVIG up to 48 hours after initiation of cell culture led to significant diminution of cell proliferation at 96 to 120 hours. This effect was dose dependent, with 10 mg/mL being the most effective and doses under 0.1 mg/mL having minimal effect. IVIG diminished the number of stimulated cells progressing in the cell cycle by 30%, and there was no difference in cell viability between IVIG-treated and IVIG-untreated cells. The production of IgE in culture by anti-CD40/IL4-stimulated B lymphocytes was curtailed by greater than 80% after addition of 5 mg/mL IVIG. This was associated with a decrease in IgE (epsilon) transcripts in IVIG-treated cultures. CONCLUSION: These data indicate that diminution of IgE production in anti-CD40/IL-4-stimulated B cells by IVIG is due to inhibition of early events related to proliferation and progression in the cell cycle.

To E or not to E? Can an IL-4-induced B cell choose between IgE and IgG4?

Parasite immunologists had known for some time that IgE-mediated hypersensitivity reactions are rare in patients with chronic helminth infections, even though basophils and mast cells in these patients are sensitized with antiparasite IgE and exposed, often continuously, to parasite antigens. The inhibition of allergic reactivity in chronic helminth infections is mainly due to IgG4 'blocking antibodies' in the serum of the infected individual. IgG4 do not fix complement and bind weakly to Fcgamma receptors. Thus, antigen binding by IgG4, unlike IgE, is likely to have no or minimally harmful consequences. The discovery that, similar to IgE, expression of IgG4 is IL-4-dependent and is an intermediate step in sequential switching from IgM to IgE makes it imperative to understand how the two isotypes are coregulated and whether the two responses can be uncoupled, selectively boosting IgG4 over IgE. The ultimate goal is to apply to allergy the lesson we learnt from helminth infections.

Adjuvant is the major parameter influencing the isotype profiles generated during immunization with a protein antigen, the Schistosoma mansoni Sm28-GST.

We have previously shown that immunization of mice with the vaccine candidate, the 28-kDa glutathione-S-transferase of Schistosoma mansoni (Sm28-GST), in alum or complete Freund's adjuvant, or with recombinant Salmonella typhimurium expressing Sm28-GST, induced type 2, mixed, or type 1 immune responses, respectively. In the present study we examined whether the genetic background, the dose and the route of antigen administration could modulate the profile of the immune response induced during these immunizations. Our results show that the nature of the adjuvant is the major factor that determines the profile of the response. Surprisingly, the genetic background did not influence the response, while the route of immunization, and to a lesser extent the dose of the antigen, weakly modulated the adjuvant-dependent orientation of the immune response.

Inhibition of experimental autoimmune myasthenia gravis by major histocompatibility complex class II competitor peptides results not only in a suppressed but also in an altered immune response.

To assess the capacity of major histocompatibility complex (MHC) class II-binding competitor peptides in inhibiting antibody-mediated disease processes, we studied experimental autoimmune myasthenia gravis in Lewis rats. Experimental autoimmune myasthenia gravis, a disease model mediated by T cell-dependent autoantibodies against acetylcholine receptors, was induced by immunization with Torpedo californica acetylcholine receptor emulsified in complete Freund's adjuvant. The immunodominant acetylcholine receptor T cell epitope was recognized by T cells in the context of MHC class II RT1.B(L). The disease inhibitory capacity of RT1.B(L)-binding peptides not related to the acetylcholine receptor was determined upon co-immunization with Torpedo acetylcholine receptor. Co-immunization of peptide OVA323-339, a strong RT1.B(L)-binding competitor peptide, resulted in complete disease inhibition. Although, the priming of the anti-acetylcholine receptor T cell response was not fully inhibited, the kinetics of the response was changed. Moreover, besides a drastic reduction of the anti-Torpedo acetylcholine receptor antibody titers, a shift in isotype distribution was found. These findings indicate that antibody-mediated autoimmune processes can be suppressed by MHC class II competitor peptides. Furthermore, the administration of such peptides in vivo not only passively inhibits T cell activation, but also functionally alters the immune response.

The immunopathology of human Schistosomiasis-III. Immunoglobulin isotype profiles and response to praziquantel.

Immunoglobulin (Ig) isotype (IgG, IgG1, IgG2, IgG3, IgG4, IgM, IgD and IgE) levels were investigated, both pre- and post-treatment with praziquantel (PZQ), in 43 adults and children chronically infected with Schistosoma mansoni, by means of a two-site, isotype-specific immunoenzymometric assay. The patients were classified as responders (R) or non-responders (NR) on the basis of their circumoval precipitin test (COPT) results 12 months after treatment. In comparison with controls, pre-treatment R children showed significantly higher levels of IgG, IgG1, IgG4 (p < 0.001) and IgE (p < 0.01); and diminished IgG2 (p < 0.05), while NR children showed significantly elevated levels only of IgE (p < 0.05). Twelve months after therapy, R children maintained significantly lower levels of IgG2, but showed significantly decreased levels of IgG, IgG1, IgG4, and IgE, while the Ig isotype profile of NR children was unaltered. Adult R and NR showed similar isotype profiles before chemotherapy, with the exception of significantly elevated IgM levels in R. Twelve months after therapy, R adults showed significantly decreased levels of IgG, IgG1, and IgG4, while NR adults showed only diminished IgG4 levels. These results reveal different Ig isotype profiles in untreated adults and children chronically infected with S. mansoni. The results further show that the pre-treatment Ig isotype profile may be significantly modified after an effective R to chemotherapy, accounted for by down regulation of the IgG1 isotype in association with negative seroconversion of the COPT in R patients. The COPT reaction has been associated with the highly specific egg glycoprotein antigen omega 1, which shows a significant reduction in reactivity six months after treatment. IgG1 may thus play a main role in the response against the omega 1 antigen.

Inhibition of TC-1 cytokine production, effector cytotoxic T lymphocyte development and alloantibody production by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a widespread environmental contaminant and prototypic ligand for the aryl hydrocarbon receptor, is a potent immunotoxicant. To understand the underlying mechanisms of TCDD immunotoxicity, we have characterized the time course of changes in CTL, alloantibody, and cytokine responses to the P815 tumor allograft in C57B1/6 mice treated with 0 or 15 microg TCDD/kg. Suppression of CTL activity by TCDD directly correlated with reduced numbers of splenic CTL effector cells identified by their CD8+CD44 high CD45RB low phenotype, while suppression of the alloantibody response correlated with a lack of expansion of the B220+ splenocyte population. Cytokine production was differentially modulated following TCDD treatment. Although type 1 cytokine production (IFN-gamma, IL-2, and TNF) was initially induced in TCDD-treated mice, production failed to increase normally after day 5. In contrast, the production of IL-1 beta, IL-4, and IL-6 was mostly unaffected by TCDD exposure. This differential effect of TCDD on cytokine production was reflected in the degree of suppression of specific alloantibody isotypes. TCDD abrogated the production of IgG2a (promoted by IFN-gamma), but had much less effect on the level of IgG1 (promoted by IL-4). IgM Ab titers were also highly suppressed. CD8+ cells were the exclusive producers of IFN-gamma and IL-2 when spleen cells from P815-injected mice were cultured in vitro on days 4 to 7 after P815 injection. However, CD4+ cells were shown to play a crucial role in the generation of both CTL and alloantibody responses, since their depletion in vivo abolished both responses. Based on similar temporal effects produced by TCDD and anti-CD4 Ab on alloimmune responses, we postulate that TCDD interferes with the initial activation of CD4+ T cells, which leads to downstream inhibition of the activation and/or differentiation of CD8+ T cells and B cells. In addition, since delayed treatment with either anti-CD4 Ab or TCDD suppressed the alloantibody but not the CTL response, TCDD may also affect later CD4+ T helper-B cell interactions.

Mechanisms of inhibition of IgE synthesis by nedocromil sodium: nedocromil sodium inhibits deletional switch recombination in human B cells.

IgE synthesis requires IL-4 and a T cell-B cell interaction that involves the B-cell antigen CD40 and its ligand expressed on activated T cells. Nedocromil sodium (NS), an effective prophylactic agent in asthma, inhibits IgE synthesis by human B cells. In this report we examined the mechanisms of this inhibition. NS targeted the B cells because it inhibited IgE synthesis induced by anti-CD40 and IL-4 in highly purified B cells (greater than 98% CD19+). NS had no effect on the induction of epsilon-germline transcripts by IL-4 but strongly inhibited CD40-mediated S mu --> S epsilon deletional switch recombination. The effect of NS was not specific for CD40 because it inhibited IgE synthesis in B cells stimulated with hydrocortisone plus IL-4. Moreover, the effect of NS was not specific for IgE because it inhibited CD40/IL-4-driven IgG4 synthesis by B cells sorted for lack of surface expression of IgG4. NS caused only modest inhibition of spontaneous IgE synthesis by B cells from patients with hyper-IgE syndrome, suggesting that it has little effect on B cells that have already undergone isotype switching. These results strongly suggest that NS inhibits IgE isotype switching by inhibiting deletional switch recombination and that NS has a novel potential mechanism for the prevention of asthma and other allergic diseases.