Long-term anergy in orally tolerized mice is linked to decreased B7.2 expression on B cells

Durable antigen (Ag)-specific T- and B-cell anergy induced by oral tolerance is an attractive strategy for immunotherapy of allergic diseases. Here, we address the lasting effect of oral tolerance induction in na?ve or primed mice to ovalbumin (OVA) on antibody production. Single feeding with OVA prior to immunization or double feeding, before and after Ag priming, in A/Sn mice, induced a long-lasting suppression of IgE, IgG1 and IgG2a responses up to 8 months after immunization. In contrast, primed-fed mice had transient IgE inhibition. Naive and double-treated mice showed marked Ag-specific unresponsiveness and scarce cytokines production. Inhibition of IL-2 and IFN-gamma secretion in na?ve-fed mice were restored in the presence of anti-CD28 mAb plus Ag stimulation. The durable inhibition of Ab production in OVA-fed mice was related to the persistent decrease of B7.2 expression on B cells. Ag feeding in naive and primed status may be a prophylactic measure to avoid later Ag sensitization.     

High-dose oral tolerance prevents antigen-induced eosinophil recruitment into the mouse airways

We have previously shown that antigen-induced eosinophil recruitment into the tissue of sensitized mice is mediated by CD4+ T cells and IL- 5. To determine whether the induction of oral tolerance down-regulates antigen-induced eosinophil recruitment into the tissue, we studied the effect of oral administration of a protein antigen on antigen-induced eosinophil infiltration in the trachea of sensitized mice, on antigen- induced CD4+ T cell infiltration and IL-5 production in the airways, and on the in vitro production of IL-2, IL-4, IL-5 and IFN-gamma in spleen cells of the mice. Oral administration of a protein antigen in high doses inhibited antigen-induced eosinophil infiltration in the trachea and IgE antibody production in mice in an antigen-specific manner. The oral administration of antigen also suppressed both CD4+ T cell recruitment into the trachea and IL-5 levels in the bronchoalveolar lavage fluids of the mice after antigen inhalation. In vitro antigen-induced production of IL-2, IFN-gamma, IL-4 and IL-5 was decreased in spleen cells of antigen-fed mice, indicating the induction of both Th1 and Th2 cell tolerance in vivo. On the other hand, pretreatment with anti-transforming growth factor-beta antibody at the time of immunization with antigen had no significant effect on the inhibition of antigen-induced eosinophil recruitment and IgE antibody production in antigen-fed mice. Finally, antigen-specific CD4+ T cells were not deleted in TCR transgenic mice after antigen feeding by FACS analysis. Taken together, these results indicate that high-dose oral tolerance induces not only Th1 but also Th2 cell tolerance in vivo and thereby inhibits antigen-induced eosinophil recruitment into the tissue.      

Adjuvant effect of zinc oxide on Th2 but not Th1 immune responses in mice

Background and aim: We investigated the effect of zinc oxide (ZnO) on Th1 and Th2 immune responses in mice.

Material and methods: Mice were intraperitoneally administered with ovalbumin (OVA) with or without varying doses of ZnO (day 0). On day 21, anti-OVA IgG, IgG2a, IgG1, and IgE antibodies in sera, OVA-specific proliferative responses of spleen cells, and production of Th1 cytokines including IFN-γ as well as Th2 cytokines such as IL-4 and IL-5 were measured.

Results: The results showed that administration of OVA with ZnO was followed by greater increases in anti-OVA IgG and the antigen-specific splenocyte proliferation compared to that of OVA alone. The production of anti-OVA IgG1 and IgE and secretion of IL-4 and IL-5 were markedly enhanced by ZnO. The enhancing effect of ZnO on these Th2 responses was as strong as aluminium hydroxide (Alum) that was widely used as an adjuvant. In contrast, treatment with OVA plus ZnO failed to affect production of anti-OVA IgG2a as well as IFN-γ. It was also observed that ZnO had a stimulating effect on the secretion of the proinflammatory cytokine IL-17 from a new lineage of effector Th cells.

Conclusion: These results suggest that ZnO appears to have an adjuvant effect on the immune system, especially Th2 but not Th1 immune responses.     

Roles of CD4+ and CD8+ T cells in adjuvant activity of diesel exhaust particles in mice

Through an imbalance in Th1 and Th2 cytokine profiles, diesel exhaust particles (DEP) are thought to induce Th2-dominated IgE and IgG1 production. However, the roles of CD4+ and CD8+ T-cell subtypes in the increased immune responses to antigen in mice exposed to DEP are unclear. In the present study, we investigated whether treatment with anti-CD4 or anti-CD8 mAb abrogated the adjuvant activity of DEP. On day -1 and day 1, each group of mice was injected intraperitoneally with anti-CD4, anti-CD8, or rat IgG (vehicle). On day 0, the mice were immunized with ovalbumin (OVA) or OVA plus DEP. After 3 weeks, each mouse was boosted with 10 microg of OVA alone. On day 7 after the first injection with OVA+DEP or OVA alone, the numbers of total, IA+, CD80+/IA+ and CD86+/IA+ cells in peritoneal exudate cells (PEC) were higher in OVA+DEP-immunized mice than in OVA-immunized mice. Depletion of CD8+ cells resulted in a modulation of the production of granulocyte-macrophage colony-stimulating factor, IL-12 and PGE(2) in peritoneal exudate fluid from OVA+DEP-immunized mice. On day 28, DEP injection markedly increased IL-4 production in the culture supernatants of spleen cells from CD4+ or CD8+-depleted mice. Depletion of CD8+ cells in OVA+DEP-immunized mice resulted in a decrease in IFN-gamma production compared with that in OVA-immunized mice. Adjuvant activity of DEP was observed in anti-OVA IgE, anti-OVA IgG1, anti-OVA IgG3, and total IgE production. Depletion of CD4+ T cells abrogated the adjuvant effect of DEP on anti-OVA IgE, and anti-OVA IgG1 production in plasma. However, depletion of CD8+ T cell inhibited the upregulated anti-OVA IgG3 production. These findings suggest that DEP injection may affect not only the function of CD4+ cells but also that of CD8+ T-cell subsets to modulate the synthesis of proinflammatory cytokine in PEC and type-1 and type-2 cytokine production in spleens.     

Ovalbumin-specific IgE modulates ovalbumin-specific T-cell response after repetitive oral antigen administration

BACKGROUND: Some patients outgrow their food allergies even though their serum antigen-specific IgE levels remain high. OBJECTIVE: To elucidate the role of T cells in outgrowing food allergies in the presence of antigen-specific IgE, we tracked antigen-specific T-cell responses after oral antigen administration. METHODS: Ovalbumin (OVA)-specific T-cell receptor (TCR) and OVA-specific IgE transgenic (Tg) mice (OVA-TCR/IgE-Tg) and OVA-specific TCR Tg (OVA-TCR-Tg) mice were fed with high doses of OVA or PBS every other day. After 7 administrations, OVA-specific proliferation and cytokine production of mononuclear cells of the spleen, mesenteric lymph nodes, and Peyer's patches and the number of splenic CD4 + CD25 + T cells were analyzed. RESULTS: Without OVA administration, the splenocytes from OVA-TCR/IgE-Tg mice exhibited a higher proliferative response and produced more IL-4 and IL-10 and less IFN-gamma than those from OVA-TCR-Tg mice. The proliferative responses of the splenocytes from either OVA-TCR/IgE-Tg mice or OVA-TCR-Tg mice fed with OVA were significantly reduced compared with those from PBS-fed mice. The number of OVA-specific TCR + T cells decreased in the spleen from OVA-fed mice, whereas the number of CD4 + CD25 + T cells increased. The suppressed proliferation of splenocytes of OVA-fed mice was partially resumed by neutralization of TGF-beta1, but not of IL-10. CONCLUSION: The presence of OVA-specific IgE modulated the OVA-specific responses of the splenocytes. Irrespective of the presence of OVA-specific IgE, repetitive oral administration of OVA induced tolerance, which seems to be composed of clonal deletion/anergy and TGF-beta1-mediated active suppression.     

Chemical Denaturation of Ovalbumin Abrogates the Induction of Oral Tolerance of Mouse Reaginic Antibody Responses

The effect of chemical denaturation of ovalbumin (OVA) on the induction of oral tolerance of reaginic antibody responses was studied. Both urea-denatured OVA (UD-OVA) and carboxymethylated UD-OVA (CM-OVA) were purified by centrifugation. When compared with OVA and UD-OVA, CM-OVA had the least sensitizing capacity and allergenicity in IgE responses to OVA. BALB/c IgE, IgG1 and IgG antibody responses were suppressed by OVA, but not by UD-OVA or CM-OVA, fed prior to sensitization with OVA, UD-OVA, or CM-OVA in alum, respectively. The priming effect of specific IgG and IgG1 antibody responses was induced by CM-OVA fed prior to sensitization with OVA or CM-OVA. The proliferation of BALB/c spleen cells and their secretion of T helper type 2 (Th2) cytokines interleukin-4 (IL-4) and IL-5 were also orally tolerized by OVA, but not by denatured OVA. Although denatured OVA is hypoallergenic, the present result indicates that denaturation of a soluble protein prevents the induction of oral tolerance of Th2 responses.     

Differential capacity of CD8α+ or CD8α− dendritic cell subsets to prime for eosinophilic airway inflammation in the T-helper type 2-prone milieu of the lung

BACKGROUND: Different subsets of dendritic cells (DCs), identified in mouse spleen by their differential expression of CD8 alpha, can induce different T-helper (Th) responses after systemic administration. CD8 alpha(-) DCs have been shown to preferentially induce Th type 2 (Th2) responses whereas CD8 alpha(+) DCs induce Th1 responses. OBJECTIVE: To study if these DC subsets can still induce different Th responses in the Th2-prone milieu of the lung and differentially prime for eosinophilic airway inflammation, typical of asthma. METHODS: Donor mice first received daily Flt3L injections to expand DC numbers. Purified CD8 alpha(+) or CD8 alpha(-) splenic DCs were pulsed with ovalbumin (OVA) or phosphate-buffered saline and injected intratracheally into recipient mice in which carboxyfluorescein diacetate succinimidyl ester-labelled OVA-specific T cell receptor transgenic T cells had been injected intravenously 2 days earlier. T cell proliferation and cytokine production of Ag-specific T cells were evaluated in the mediastinal lymph nodes (MLNs) 4 days later. The capacity of both subsets of DCs, to prime for eosinophilic airway inflammation was determined by challenging the mice with OVA aerosol 10 days later. RESULTS: CD8 alpha(-) DCs migrated to the MLN and induced a vigorous proliferative T cell response accompanied by high-level production of IL-4, IL-5, IL-10 and also IFN-gamma during the primary response and during challenge with aerosol, leading to eosinophilic airway inflammation. In the absence of migration to the MLN, CD8 alpha(+) DCs still induced a proliferative response with identical levels of IFN-gamma but reduced Th2 cytokines compared with CD8 alpha(-) DCs, which led to weak eosinophilic airway inflammation upon OVA aerosol challenge. Unpulsed DCs did not induce proliferation or cytokine production in Ag-specific T cells. CONCLUSION: CD8 alpha(-) DCs are superior compared with CD8 alpha(+) DCs in inducing Th2 responses and eosinophilic airway inflammation in the Th2-prone environment of the lung.     

Suppression of asthma-like responses in different mouse strains by oral tolerance

In this study we examined the effect of oral antigen (Ag) administration on the development of experimental asthma in different mouse strains. We selected BALB/c, BP2, CBA/Ca interleukin (IL)-5 transgenic, and BALB/c T-cell receptor-delta-deficient mouse strains because they exhibit different aspects of the asthma syndrome. Mice exposed to 1% ovalbumin (OVA), dissolved in the drinking water for 5 consecutive days, became unresponsive to subsequent immunogenic OVA challenges. This regimen of OVA administration induced Ag-specific unresponsiveness in all mouse strains tested, including gammadelta-deficient mice that are said to be resistant to tolerance induction. The Ag-specific unresponsiveness was characterized by reduced (almost absent) airway eosinophilic inflammation, airway hyperreactivity, and mucus production; also by low levels of T helper (Th) 2-type cytokines in bronchoalveolar lavage fluid, and decreased immunoglobulin (Ig) G1 and IgE OVA-specific antibody production. The unresponsive state was not associated with increased levels of the suppressive cytokines IL-10 and transforming growth factor (TGF)-beta or with immune deviation toward the Th1 pathway due to increased levels of interferon-gamma and IL-12. Moreover, treatment with anti- TGF-beta antibodies did not abrogate oral tolerance. Oral Ag administration was quite effective in suppressing the development of key features of asthma when initiated after primary immunization (Day 0) or after booster (Day 7), but not after challenge (Day 14) when it increased allergic responses. Collectively, our findings show for the first time the beneficial and detrimental effects of oral Ag administration on the development of experimental asthma.     

Massive production of Th2 cytokines by human CD4+ effector T cells transiently expressing the natural killer cell marker CD57/HNK1.

We have reported previously that uncommitted human CD4+ CD45RO- T cells default to the T-helper type 1 (Th1) pathway, if they are costimulated by anti-CD3 plus anti-CD28 monoclonal antibodies (mAb). In contrast, 5% of the uncommitted T cells differentiate into Th2 cells, if they are stimulated by anti-CD28 plus interleukin-2 (IL-2) in the absence of T-cell receptor (TCR) signals. The anti-CD28/IL-2-induced proliferation (and the resulting Th2 commitment) was not affected by neutralizing anti-IL-4 mAb, suggesting a non-conventional IL-4-independent Th2 differentiation pathway. Here we report that the respective CD4+ Th2 cells (but not the Th1 cells) coexpressed the natural killer (NK) cell marker HNK1/CD57. Expression of CD57 on Th2 cells required CD28 stimulation, and was suppressed by CD3/TCR signals. However, Th2 effector cells displayed a TCR V beta-chain usage comparable to that of committed Th1 cells (with V beta 8 dominating). Our data suggest that expression of CD57 on human CD4 T cells may be associated with defined stages of Th2 cell activation/differentiation, and may not necessarily characterize a separate T-cell lineage. The induction of cytokine production and B-cell helper function in both Th1 and Th2 populations required CD3/TCR signalling in costimulation with anti-CD28 or IL-2. Importantly, anti-CD28/IL-2-primed Th2 cells readily secreted IL-4 and induced IgE production by surface IgE- B cells in response to the first TCR signal and independent of previous contact with IL-4. Therefore, CD4+ CD57+ T cells responded comparably to murine CD4+ NK1.1+ T cells, which are critical for the development of Th2/IgE immune responses in vivo. The possible role of human CD4+ CD57/HNK1+ Th2-like cells in cancer, infection and allergy is discussed.     

Interleukin-10 and antigen-presenting cells actively suppress Th1 cells in BALB/c mice infected with the filarial parasite Brugia pahangi

Infection with the third-stage larvae (L3) of the filarial nematode Brugia results in a Th2-biased immune response in mice and humans. Previously we have shown that the production of interleukin 4 (IL-4) is critical for down-regulating polyclonal Th1 responses in L3-infected mice. However, the in vitro neutralization of IL-4 did not fully recover the defective polyclonal Th1 responses, nor did it result in the production of any antigen (Ag)-specific Th1 cytokines, suggesting that perhaps infection with L3 does not result in priming of Th1 cells in vivo. In this study, we analyzed the role of IL-10 and Ag-presenting cells (APCs) in the spleen as additional factors controlling the Th2 bias in infected mice. Our data show that IL-10 and APCs also contribute to the suppression of mitogen-driven Th1 responses of spleen cells from infected mice. In addition, the neutralization of IL-10 or the replacement of the resident APC population from spleen cell cultures resulted in the production of Ag-specific Th1 cytokines. Irradiated spleen cells from either L3-infected or uninfected mice were able to restore Ag-specific Th1 responses in vitro. Therefore, it appears that Brugia-reactive Th1 cells are primed following infection with L3, but are actively suppressed in vivo by a mechanism that involves IL-10 and the resident APC population, but not IL-4. These results indicate that a complex interplay of cytokines and cell populations underscores the Th2-polarized response in L3-infected mice.     

The influence of dietary protein antigen on Th1/Th2 balance and cellular immunity.

Dietary administration of ovalbumin (OVA) antigen (Ag) into OVA-specific T cell receptor alphabeta-transgenic (TCR-Tg) mice resulted in the induction of activated CD4+ Th cells expressing CD69 early activation Ag. However, the number of CD4+ Th cells rather decreased by dietary administration of OVA antigen. The production of Th1-cytokines such as IFN-gamma and IL-2 markedly reduced in spleen of OVA-fed mice compared to mice fed with normal diet. In sharp contrast, the production of Th2-cytokine, IL-4 greatly increased in spleen of OVA-fed mice though the number of CD4+ T cells decreased to less than 10% of control mouse spleen. The decrease of IFN-gamma production and the increase of IL-4 production by CD4+ T cells was demonstrated at a single cell level by intracellular cytokine staining analysis. Moreover, such a polarized cytokine production pattern was also demonstrated using highly purified CD4+ T cells obtained from mice fed with OVA. In addition to the decrease of Th1-cytokine production, TCR-Tg mice fed with OVA-containing diet showed greatly reduced in vivo generation of NK cells, LAK cells and CTL. These results suggested that dietary protein antigen caused the polarization of Th1/Th2 balance into Th2-dominant immunity and inhibited cellular immunity.     

Increased susceptibility to airway responses in CD40-deficient mice

The interaction between CD40 and its ligand (CD154) is crucial for IL-12 production and effective humoral immunity such as IgE production. Although the interaction seems to play a crucial role in asthmatic inflammation, previous studies investigating the role of the CD40 and CD154 interaction in experimental animal models of asthma are complicated due to multistep reactions in developing asthma. Here, in order to investigate the role of CD40 in the effector phase in the development of airway responses, we used CD40-deficient mice backcrossed with mice transgenic for an ovalbumin (OVA)-specific TCR (TCRtg). Using intranasal OVA administration followed by aerosol inhalation of OVA, greater airway hyperreactivity and eosinophilia in bronchoalveolar lavage fluid (BALF) were observed in CD40-deficient mice backcrossed with TCRtg mice (CD40-/-/ TCRtg mice), compared with control littermates (CD40+/+/ TCRtg mice). CD4+ helper T cell subset analysis of lung draining lymph nodes revealed that the Th1 component was significantly decreased in CD40-/-/ TCRtg mice. Airway hyperreactivity and airway eosinophilia significantly correlated with the predomination of Th2 cells. Cytokine measurements in BALF also showed decreased IL-12 and the predominance of Th2 cells in CD40-/-/ TCRtg mice. These results suggest that CD40 may play a protective role in developing asthma in the phase after establishing specific memory T cells through the regulation of the balance between Th1 and Th2 cells presumably via induction of IL-12.     

Anti-interleukin-4 modulation of the Th2 polarized response to the parasitic nematode Brugia pahangi.

Lymphatic filariasis is a chronic disease characterized by a pronounced Th2 bias in the immune response and impaired antigen (Ag)-specific Th1 responses. We have used a mouse model of filariasis to investigate the role of the infective form (the third-stage larvae [L3]) in modulating the immune response. Subcutaneous infection of BALB/c mice with L3 of Brugia pahangi has a profound effect on Th cell function. By day 12 post-infection, spleen cells from these mice exhibited a dramatic reduction in concanavalin A-driven proliferation and interleukin-2 (IL-2) and gamma interferon (IFN-gamma) secretion in comparison with uninfected controls. However, exposure to L3 did not render the mice completely unresponsive; these animals mounted a strong Th2 response to the parasite, characterized by elevated levels of IL-4, IL-5, and IL-10 and parasite-specific serum immunoglobulin G (IgG), IgG1, and IgE. Treatment of spleen cells from L3-infected mice with neutralizing anti-IL-4 or recombinant IL-2 resulted in a dramatic increase in concanavalin A-induced proliferation and IL-2 and IFN-gamma production. Despite their defective polyclonal Th1 response, cells from L3 infected mice proliferated when stimulated with Ag, and this response was blocked by anti-IL-4. However, anti-IL-4 treatment failed to induce Ag-specific IL-2 or IFN-gamma production, indicating that B.pahangi-primed Th1 cells do not appear to be present or are still unable to respond even in the absence of IL-4.     

In vivo immunologic intervention in age-related T cell defects in murine gut-associated lymphoid tissues by IL2

Our recent studies indicate that the aging process impairs gut mucosal humoral immune responses to mycobacterial antigen (Ag), largely owing to defects in T cell function--in particular, that of suppressor T cells. To correct the age-associated Ag-specific T cell-mediated immune alteration recombinant IL2 (50,000 units/s.c./mouse/day) was administered for 3 weeks to the aged (greater than 24 months) mice (BALB/c), which were divided into 4 groups (Gr) [Gr. 1, fed intragastrically (i.g.) with saline; Gr. 2, immunized i.g. with Mycobacterium paratuberculosis (M. paratbc) protoplasmic Ag; Gr. 3, administered IL2 alone; Gr. 4, immunized i.g. with the Ag and given IL2]. In addition, young adult mice were also grouped and treated as the aged. First, we examined the effect of exogenous IL2 on Ag-specific immunoglobulin (Ig) production by gut-associated lymphoid tissues (GALT) (Peyer's patches, PP; mesenteric lymph nodes, MLN) and non-GALT (spleen, SPN) cells. Aged Gr. 4 (treated with both Ag and IL2) GALT and SPN unfractionated cells showed significantly reduced production of Ag-specific IgM, IgG, and IgA, as compared to aged Gr. 2 (treated with Ag alone) cells. Second, in co-culture experiments with aged T and B cells, aged GALT-derived CD8+ suppressor T (Ts)-depleted T cell subsets of Gr. 4 helped Ag-specific IgM and IgA production by GALT B cells, but to a slightly lesser extent, than those of the Gr. 2. GALT CD4+ T cells of aged Gr. 4 augmented IgM and IgA production by GALT B cells nearly to the levels of the corresponding cocultures of the Gr. 2. In contrast to aged Gr. 2 cocultures, GALT CD4+ plus CD8+ cells of aged Gr. 4 decreased IgM and IgA production to a considerable extent, and in those of SPN, IgG production was also diminished. The humoral immune responses of aged unprimed Gr. 1 (treated with saline) and Gr. 3 (treated with IL2 alone) GALT and SPN cells remained almost unchanged. Similarly, in all Gr. from young adult mice, oral tolerance was maintained regardless of IL2 administration. Third, together with the deletion experiments of the Ts cells, the results of the cross experiments, in which the young adult B and CD4+ Th cells and aged CD8+ Ts cells were cocultured, clearly support the view that the corrective mechanism of the humoral immune responses in aged GALT by exogenous IL2 is attributed to the partial recovery of the Ts cell functions.(ABSTRACT TRUNCATED AT 400 WORDS)     

Selective inhibition of systemic anti-OVA IgE production in response to oral pre-treatment with OVA-liposome conjugates

BACKGROUND: We have previously reported that intraperitoneal injection with OVA-liposome conjugates induces OVA-specific and IgE-selective unresponsiveness in mice. METHODS: In the present study, the effects of oral pre-treatment with OVA-liposome conjugates or with plain OVA solution on anti-OVA IgG antibody production were investigated in mice after subsequent immunization with alum-adsorbed OVA. Control mice received only the immunization. RESULTS: The levels of serum anti-OVA IgG antibody in mice receiving oral administration of OVA-liposome were comparable to those in the control mice. However, in mice receiving oral administration of the same dose of plain OVA, levels of serum anti-OVA IgG antibody were significantly lower than those in control mice. Surprisingly, anti-OVA IgE antibody production was completely inhibited in mice receiving oral administration of OVA-liposome conjugates. Splenic CD4(+) T cells of mice receiving oral administration of OVA-liposome and those of control mice produced comparable levels of cytokines, while those of mice receiving oral administration of plain OVA solution produced significantly lower levels of cytokines than those in the other two groups. CONCLUSION: Orally administered OVA-liposome did not affect anti-OVA IgG production but did inhibit anti-OVA IgE antibody production, while orally administered OVA solution inhibited production of both IgG and IgE antibodies. These results suggest that antigen-liposome conjugates can possibly be orally administered in order to control antigen-specific IgE antibody production, without affecting IgG antibody production.     

Impaired humoral immune responses to mycobacterial antigen in aged murine gut-associated lymphoid tissues

Senescence-related alterations of local gut mucosal immune responses to enteric mycobacterial antigen (Ag) were examined. Both aged (greater than 24 months old) and young adult (4-5 months old) BALB/c mice were enterically immunized with crude Mycobacterium paratuberculosis (M. paratbc) protoplasmic Ag, and in vitro Ag- and class-specific immunoglobulin (g) production by lymphocytes from gut-associated lymphoid tissues (GALT) (Peyer's patches, PP; mesenteric lymph nodes, MLN) and non-GALT (spleen, SPN) were determined against semipurified M. paratbc Ag. Ag-specific spontaneous immunoglobulin production by aged B cells from both GALT and non-GALT was enhanced only to a minor extent. Similarly, the functional activity of the Ag-specific T (Th) (CD3+, CD4+) cell in both GALT and non-GALT was not profoundly affected by senescence (qualitative preservation). However, that of the suppressor T (Ts) (CD3+, CD8+) cell was considerably diminished (qualtative defect). Thus, oral tolerance (systemic immunologic hyporesponsiveness) to M. paratbc Ag in aged mice is impaired. These age-related changes, manifested as hyperreactive humoral responses to the enteric microbial Ag, are due, at least in part, to hyporeactivity of the Ts cell, resulting in relative hyperfunction of the Ag-specific Th cell, despite the quantitative defect of the latter cell.     

Antigen-specific, IgE-selective unresponsiveness induced by antigen-liposome conjugates. Comparison of four different conjugation methods for the coupling of antigen to liposome

BACKGROUND: We have previously reported that ovalbumin (OVA) coupled with liposome via glutaraldehyde (GA) induced OVA-specific- and IgE-selective unresponsiveness in mice. METHODS: In this study, OVA-liposome conjugates were made using four different coupling protocols: via GA, N-(6-maleimidocaproyloxy) succinimide (EMCS), disuccinimidyl suberate (DSS) and N-succimidyl-3(2-pyridyldithio)propionate (SPDP) and the induction of antigen-specific IgG and IgE antibody production was investigated for each. In addition, antigen-specific cytokine production by spleen cells of mice immunized either with OVA-liposome or with OVA adsorbed with aluminum hydroxide was investigated. RESULTS: OVA-liposome conjugates coupled via GA or DSS did not induce anti-OVA IgE antibody production but induced substantial anti-OVA IgG antibody production. On the other hand, the induction of anti-OVA IgE unresponsiveness by OVA-liposome conjugates coupled via EMCS or SPDP was incomplete. The amount of interleukin 4 (IL-4) produced by spleen cells stimulated in vitro with OVA correlated well with anti-OVA IgE antibody production in donor mice. However, the production of no other cytokine, i.e., IL-2, IL-5, IL-10 or interferon-gamma, was correlated with in vivo IgE antibody production. CONCLUSION: OVA-liposome coupled via GA or DSS induced complete suppression of anti-OVA IgE production. The results in this study further suggest that the regulation of IgE antibody production does not necessarily correlate with so-called Th1 cytokine production.     

Oral tolerance induction in dermatophagoides pteronyssinus-sensitized mice induces inhibition of IgE response and upregulation of TGF-beta secretion.

Oral antigen administration induces peripheral tolerance in naive animals. Studies of oral tolerance induction in sensitized mice have clinical relevance as a strategy to modulate allergy. In this study, the A/Sn mice sensitized with extract of Dermatophagoides pteronyssinus (Dp) and submitted to oral Dp administration showed a marked decrease in IgE anti-Dp antibody production compared with sensitized phosphate-buffered saline (PBS)-fed mice. T cells from Dp-fed mice cocultured with spleen cells from PBS-fed mice were able to inhibit IgE anti-Dp antibody production and did not interfere in IgG1 antibody levels. The analysis of cytokine profile after Dp feeding showed a significant decrease in interleukin-4 (IL-4), IL-5, and IL-13 antigen-induced secretion levels by spleen cells, without shifting to IL-2 and interferon-gamma (IFN-gamma) production. Both transforming growth factor-beta (TGF-beta) baseline and TGF-beta antigen-stimulated levels were increased in Dp-fed mice. The effects of regulatory cytokines on anti-Dp IgE antibody production were investigated in vitro. The addition of recombinant TGF-beta (rTGF-beta) to spleen cell cultures stimulated by Dp inhibited IgE antibody secretion in both mouse groups. Neutralizing antibodies to IL-4, but not anti-TGF-beta, induced a marked inhibition of IgE production. Therefore, a negative modulatory effect on IgE response by inhibition of the axis Th2 was observed in sensitized Dp-fed mice, possibly mediated by induction of regulatory cytokines.