Dietary nucleotides can up-regulate antigen-specific Th1 immune responses and suppress antigen-specific IgE responses in mice

BACKGROUND: It has been reported that dietary nucleotides enhance T helper cell activities. In this study, we have determined the effects of dietary nucleotides on antigen-specific Th1 and Th2 responses and IgE responses. METHODS: Ovalbumin (OVA)-specific T cell receptor (TCR) transgenic (OVA-TCR Tg) mice, 3 weeks old, were fed a nucleotide-free diet (NT(-) diet) or the NT(-) diet supplemented with dietary nucleotides (NT(+) diet) for 4 weeks. Cytokine production by spleen cells and macrophages obtained from these mice was measured in vitro. BALB/c mice, 3 weeks old, immunized intraperitoneally with OVA adsorbed onto alum, were fed the NT(-) diet or the NT(+) diet for 4 weeks. Serum levels of antigen-specific antibodies in the BALB/c mice were determined by ELISA. RESULTS: The level of production of antigen-specific interferon-gamma by spleen cells was significantly higher in the OVA-TCR Tg mice fed the NT(+) diet than in the control mice. The levels of secretion of bioactive IL-12 by spleen cells and peritoneal macrophages were also significantly increased in the NT(+) diet group. The serum OVA-specific IgE level was significantly decreased in BALB/c mice fed the NT(+) diet compared with those fed the NT(-) diet. CONCLUSION: These results show that dietary nucleotides up-regulate the antigen-specific Th1 immune response through the enhancement of IL-12 production and suppress the antigen-specific IgE response.     

Suppression of serum IgE response and systemic anaphylaxis in a food allergy model by orally administered high-dose TGF-beta

Some epidemiological or association studies suggest that transforming growth factor-beta (TGF-beta) in breast milk may be a decisive factor in diminishing the risk of allergic diseases during infancy. The observations have prompted us to investigate whether TGF-beta, when taken orally, can affect allergic immune responses. Repeated high-dose ovalbumin peptide (OVA) feeding was previously reported to induce OVA-specific IgE production and an anaphylactic reaction after intravenous challenge of OVA in OVA-TCR transgenic mice, which might represent a model for food allergy. By using this model, we showed here that oral administration of high-dose TGF-beta simultaneously with OVA feeding significantly inhibited the OVA-specific IgE elevation and anaphylactic reaction in OVA-TCR transgenic DO11.10 mice. These effects were associated with suppression of OVA-specific IL-4 production and GATA-3 expression and with up-regulation of IFN-gamma production and T-bet expression by splenocytes. Intra-peritoneal injection of anti-TGF-beta-neutralizing antibody abolished the inhibitory effects of orally administered TGF-beta on the serum IgE response and anaphylactic reaction after OVA feeding in DO11.10 mice. Interestingly, oral administration of high-dose TGF-beta suppressed activation-induced T cell death induced by OVA feeding in DO11.10 mice. We thus conclude that TGF-beta, when taken orally at high dose, has the capacity to modulate a food allergy-related reaction, at least in part, through its systemic activity.     

Lactobacillus casei strain Shirota suppresses serum immunoglobulin E and immunoglobulin G1 responses and systemic anaphylaxis in a food allergy model

BACKGROUND: Our previous study using allergen-sensitized murine splenocyte cultures has shown that Lactobacillus casei strain Shirota (LcS), a lactic acid bacterium widely used as a starter for fermented milk products, suppresses IgE production through promoting a dominant Th1-type response mediated by IL-12 induction. OBJECTIVE: We tried to evaluate the ability of LcS to suppress both IgE response and allergic reactions in vivo using a food allergy model with ovalbumin-specific T cell receptor transgenic (OVA-TCR-Tg) mice. METHODS: The ability of heat-killed LcS to induce IL-12 in serum was tested. OVA-TCR-Tg mice were fed a diet containing OVA for 4 weeks and injected with LcS intraperitoneally three times in the first week of this period. Cytokine and antibody secretion by splenocytes, and serum IgE and IgG1 responses were examined. The inhibitory effect of LcS on systemic anaphylaxis induced by intravenous challenge of OVA-fed OVA-TCR-Tg mice with OVA was also tested. RESULTS: Intraperitoneal injection of LcS induced an IL-12 response in the serum of OVA-TCR-Tg mice. In the food allergy model, LcS administration skewed the pattern of cytokine production by splenocytes toward Th1 dominance, and suppressed IgE and IgG1 secretion by splenocytes. The ability of LcS to modulate cytokine production was blocked by anti-IL-12 antibody treatment. LcS also inhibited serum OVA-specific IgE and IgG1 responses and diminished systemic anaphylaxis. CONCLUSION: LcS administration suppresses IgE and IgG1 responses and systemic allergic reactions in a food allergy model, suggesting a possible use of this lactic acid bacterium in preventing food allergy.     

Helper CD4+ T cells for IgE response to a dietary antigen develop in the liver

BACKGROUND: Although T-cell responses to food antigens are normally inhibited either by deletion, active suppression, or both of antigen-specific T cells, T helper cells for IgE response to a food antigen still develop by unknown mechanisms in a genetically susceptible host. OBJECTIVE: We determined the site at which those IgE helper T cells develop. METHODS: We administered ovalbumin (OVA) orally to DO11.10 mice and studied CD4+ T cells in Peyer's patches, the spleen, and the liver. Helper activity for IgE response was assessed by adoptively transferring those CD4+ T cells to naive BALB/c mice, followed by systemic immunization with OVA. RESULTS: OVA-specific CD4+ T cells were deleted by cell death in the liver and Peyer's patches of DO11.10 mice fed OVA. OVA-specific CD4+ T cells that survived apoptosis in the liver expressed Fas ligand and secreted IL-4, IL-10, and transforming growth factor beta(1). CD4+ T cells producing IFN-gamma were deleted in the liver by repeated feeding of OVA. On transfer of CD4+ T cells to naive mice and systemic immunization with OVA, a marked increase in OVA-specific IgE response developed only in the mice that received hepatic CD4+ T cells from OVA-fed mice, the effect of which was not observed in the recipients of hepatic CD4+ T cells deficient in IL-4. In addition, significant suppression of delayed-type hypersensitivity and IgG(1)/IgG(2a) responses to OVA was observed in the recipients of hepatic CD4+ T cells, and this suppression required Fas/Fas ligand interaction. CONCLUSION: Together, these results suggested that a food antigen might negatively select helper T cells for IgE response to the antigen by preferential deletion of T(H)1 cells in the liver.     

Intranasal treatment with ovalbumin but not the major T cell epitope ovalbumin 323–339 generates interleukin-10 secreting T cells and results in the induction of allergen systemic tolerance

BACKGROUND: Nasal administration of major peptide T cell epitopes gives contradictory data on the induction of peripheral tolerance. OBJECTIVE: To compare the prophylactic effect of intranasal treatment (INT) on the development of an allergic response, using either ovalbumin (OVA) or its major T cell epitope OVA 323-339 (OVAp). METHODS: BALB/c mice were treated intranasally with OVA or OVAp and subsequently immunized s.c. with OVA. Anti-OVA-specific antibody, T cell proliferation and cytokine responses were analysed. In an adoptive transfer model using OVAp specific TCR transgenic (Tg) T cells from D011.10 mice, in vivo tracking and characterization of transferred T cells in the cervical, inguinal and bronchial lymph nodes (BLN) and in the spleen were determined by FACS analysis. RESULTS: Prophylactic INT with OVA induced T cell tolerance towards subsequent OVA s.c. immunizations, inhibiting OVA specific T cell proliferation, IgE and IgG1 production, in contrast to INT with OVAp, which was unable to induce tolerance. In vivo analysis of transferred OVA-specific TCR Tg T cells showed that INT with OVA induced a preferential activation of T cells in BLN, as opposed to a broad, systemic activation with OVAp. In vivo, OVAp INT led to faster and more sustained cell division cycles than OVA INT. Ex vivo, tolerance to OVA was associated with the generation of IL-10 secreting CD4(+) T cells in BLN of OVA-treated mice only. CONCLUSION: INT with OVA but not with OVAp led to regional (as opposed to systemic) T cell activation and the induction of IL-10 secreting CD4(+) T cells in BLN, potentially critical steps in the induction of T cell-specific tolerance via the nasal route.     

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.     

Sublingual 'oral tolerance' induction with antigen conjugated to cholera toxin B subunit generates regulatory T cells that induce apoptosis and depletion of effector T cells

Sublingual (s.l.) immunotherapy has in the last decade emerged as an effective approach to desensitize patients with pollen, food and insect sting allergies. This treatment has recently also attracted interest as a potential modality to control self-reactive T-cell responses associated with autoimmune disorders. Here, we show that s.l. administration of ovalbumin (OVA) conjugated to cholera toxin B subunit (CTB) (OVA/CTB) can efficiently suppress peripheral effector T (Teff) cell responses to OVA in mice that had adoptively received OVA-specific T-cell receptor (TCR) transgenic CD4(+) T cells, and that the suppression was associated with the development of OVA-specific Foxp3(+)CD25(+)CD4(+) regulatory T (Treg) cells as well as with apoptosis (Annexin V(+)) and depletion of OVA-specific Teff cells in peripheral lymph nodes. The induction of Teff cell apoptosis by s.l. OVA/CTB administration was found to be critically dependent on CD25(+) Treg cells but independent of IL-10 production. Our results suggest that s.l administration of a CTB-conjugated antigen can efficiently induce peripheral Teff cell tolerance through the induction of antigen-specific Treg cells that both inhibit Teff cell proliferation and cytokine production and induce Teff cell apoptosis and depletion.     

Serum IgE response to orally ingested antigen: a novel IgE response model with allergen-specific T-cell receptor transgenic mice

BACKGROUND: The mechanism by which orally ingested allergens elicit an IgE response remains unclear because there are few animal models available for investigation of this response. OBJECTIVE: We tried to develop a murine model suitable for investigation of the IgE response to orally ingested allergens, which would allow us to identify T cells that could promote IgE production. METHODS: Ovalbumin (OVA)-specific T-cell receptor transgenic mice were fed a diet containing OVA, and both the serum antibody response and cytokine production by splenocytes were examined. RESULTS: Oral administration of OVA to transgenic mice led to an increase in the levels of both antigen-specific IgE and total IgE in the sera. Subsequent intravenous challenge of OVA-fed transgenic mice with OVA resulted in anaphylactic shock. Analysis of cytokine production by splenocytes revealed that high IL-4-producing T cells appeared in the spleen 1 week after the start of feeding the OVA diet. T cells from these mice were found to promote IgE secretion by BALB/c B cells in vitro. This helper activity and the levels of IL-4 secretion were diminished after long-term feeding. These findings suggest the possibility that the orally ingested antigen elicited a response by a subpopulation of T cells that produce high levels of T(H2)-type cytokines and that promote IgE secretion, and these same T cells were tolerized by the orally ingested antigen. CONCLUSION: This experimental model with transgenic mice may be a useful tool for further studies of the cellular and molecular mechanisms of the T-cell and IgE responses to orally ingested antigens.     

Efficient induction of an antigen-specific, T helper type 1 immune response by interleukin-12-secreting fibroblasts

To determine whether the paracrine secretion of interleukin (IL)-12 can efficiently convert immune responses characterized by high levels of synthesis of IL-4 and immunoglobulin E (IgE) into T helper 1 (Th1)-dominated responses, 3T3 fibroblasts were stably transfected to secrete IL-12 (480 units/10(6) cells/48 hr). Their effects on the T helper cell-mediated immune response were investigated in ovalbumin (OVA)-primed mice. Free mouse recombinant IL-12 was included as a control group. IL-12-secreting fibroblasts (3T3/IL-12) were more effective than free recombinant IL-12 at increasing OVA-specific interferon-gamma (IFN-gamma) production and decreasing OVA-specific IL-4 production in CD4+ T cells. In addition, injection with 3T3/IL-12 cells significantly increased anti-OVA immunoglobulin G2a (IgG2a) levels and decreased anti-OVA IgE levels in OVA-primed mice. This work suggests that IL-12-secreting fibroblasts can efficiently induce an antigen-specific Th1 response and may be beneficial in the treatment of diseases caused by undesirable T helper 2 (Th2)-dominated responses, including allergic diseases.     

Limiting dilution analysis of CD4 T-cell cytokine production in mice administered native versus polymerized ovalbumin: directed induction of T-helper type-1-like activation.

Polarized expression of T-helper type-1 (Th1)- or Th2-like patterns of cytokine production frequently correlates with disease outcome. Previously, we have described the long-lived reciprocal regulation of ovalbumin (OVA)-specific IgE (> 95% inhibition) and IgG2a (300-800-fold increased) production following administration of high MW OVA polymers (OVA-POL), in both de novo and ongoing OVA (alum)-induced responses. Here, limiting dilution analysis (LDA) was used to compare precursor frequencies of CD4 T cells producing interferon-gamma (IFN-gamma), interleukin-4 (IL-4) or IL-10 following OVA versus OVA-POL exposure in vivo. Adjuvants were not used, so as to circumvent their impact on measurement of precursor frequencies. We found that the two forms of antigen elicited T-cell activation of comparable intensity, as indicated by equivalent precursor frequencies of clonogenic antigen-specific CD4 T cells. However, they elicited qualitatively different cytokine responses. OVA-POL treatment led to 10-fold higher (mean of six independent LDA experiments) frequencies of IFN-gamma-producing cells, and a mean fivefold lower frequency of IL-10-producing cells, than was observed following in vivo administration of unmodified OVA. Thus, the high MW polymerized form of antigen acted to steer commitment of naive (for this antigen) CD4 T-cell activation from a situation in which IL-10 producers outnumbered IFN-gamma-producing cells by a factor of 4:1 (found in mice administered OVA), to one where IFN-gamma producers dominated by a factor of 11:1 (in mice given OVA-POL), i.e. a qualitative shift in the nature of the OVA-specific response induced from Th2-like to Th1-like. In vivo co-administration of anti-IFN-gamma monoclonal antibody (mAb) abolished the capacity of OVA-POL to preferentially elicit Th1-like dominance. Interestingly, although the ratios of IFN-gamma:IL-4 and IFN-gamma:IL-10 OVA-specific precursor frequencies were strongly increased following OVA-POL exposure (mean 18- and 47-fold higher), the frequency of IL-4-producing CD4 T cells did not differ significantly. The data suggest that this modified antigen promotes in vivo commitment of naive T cells towards a Th1-like response, with consequent inhibition of IgE and enhancement of IgG2a responses, not through direct effects on IL-4 production, but via decreased frequencies of IL-10 and increased frequencies of IFN-gamma-producing OVA-specific CD4 cells. Collectively, the data (1) demonstrate the ability to manipulate commitment of antigen-driven CD4 T-cell populations in naive mice to specific patterns of cytokine gene expression, and (2) provide in vivo evidence of the regulatory role played by IFN-gamma in limiting induction and/or expansion of IL-4- and IL-10-producing CD4 cells to protein allergens.     

TCR transgenic CD8+ T cells activated in the presence of TGFbeta express FoxP3 and mediate linked suppression of primary immune responses and cardiac allograft rejection

Although CD4+CD25+FoxP3+ regulatory T cells play a role in allograft tolerance, the role of CD8+ cells with immunosuppressive function is less clear. To address this issue, spleen cells from Rag-1-deficient TCR transgenic (Tg) mice expressing a receptor for ovalbumin (OVA) in the context of MHC class I (OT1) were activated with OVA expressing antigen-presenting cell (APC) in the presence or absence of exogenous transforming growth factor beta (TGFbeta). TGFbeta inhibited the expression of IFN-gamma, granzyme B and the lytic activity of the OT1 T cells while inducing FoxP3 expression in 5-15% of the cells. By contrast, FoxP3 expression was not detected in naive OT-1 T cells or OT-1 T cells activated without exogenous TGFbeta. TGFbeta-activated OT1 cells inhibited the activation of Kd-specific CD8+ CTL responses by normal B6 T cells and the proliferation by Kd-specific CD4+ TCR Tg T cells, but only if the OVA epitope was co-expressed by Kd+ APC. This antigen-specific inhibitory activity, referred to as linked suppression, was neither mediated by residual lytic activity within the activated OT1 T cells nor did it depend upon IL-10 or TGFbeta. Suppression correlated with inhibition of CD86 expression on CD11c+ APC. TGFbeta-activated OT1 T cells also delayed the rejection of heterotopic, vascularized cardiac allografts mediated by anti-Kd-specific CD4+ TCR Tg T cells, but only if the cardiac allograft expressed both OVA and Kd as transgenes. Prolonged survival of allografts was associated with rapid migration of the FoxP3+ OT1 T cells into the donor heart raising the possibility that suppression may be mediated within the allograft. These data show that TGFbeta-activated CD8+ T cells mediate antigen-specific, APC-focused patterns of suppression in vitro and in vivo.     

Food antigen causes TH2-dependent enteropathy followed by tissue repair in T-cell receptor transgenic mice

BACKGROUND: Clarification of the mechanisms underlying the development of food-sensitive intestinal inflammation will provide an important clue to combating food allergies. OBJECTIVE: To establish a model of intestinal inflammation caused by oral administration of antigen without additional treatments, we focused on the ovalbumin (OVA) 23-3 T-cell receptor transgenic mouse, which had been reported to have high serum antigen-specific IgE responses to the feeding of an egg white diet. METHODS: Changes in body weight of mice fed an egg white diet were monitored throughout the 28-day experimental period. After the 28-day feeding, intestinal tissues were harvested for histologic examination. Endogenous production of cytokines and histamine in the jejunum, and production of cytokines secreted by OVA-specific CD4+ T cells purified from mesenteric lymph nodes, were analyzed. RESULTS: Egg white diet-fed OVA23-3 mice developed weight loss and inflammation with villous atrophy and goblet cell hyperplasia, especially in the jejunum. A further characteristic feature was evidence of weight recovery and tissue repair. Jejunal inflammation was also observed in egg white diet-fed recombination activating gene (RAG)-2-deficient OVA23-3 mice. In addition, tissue sections revealed significant infiltration of specific IgE-positive cells and IgE-positive degranulating mast cells. Higher levels of IL-4 and significant levels of histamine were detected in the tissues. In the supernatant of OVA-stimulated T cells, IL-10 levels were also markedly elevated. CONCLUSION: We report that high-dose and continuous intake of primitive OVA alone induces enteropathy containing regions under repair in OVA23-3 mice. Antigen-specific T cells and inflammatory cells primed by T(H)2 responses play important roles in regulation of development and improvement of the disease. CLINICAL IMPLICATIONS: Long-term antigen intake causes T(H)2-dependent and food-sensitive enteropathy followed by tissue repair.     

抗原特异性Th17细胞的分化与调节

目的: 探讨影响抗原特异性Th17细胞分化和调节的因素.方法: T细胞受体转基因小鼠(DO11.10)CD4 T细胞, 与同背景正常小鼠的脾细胞混合, 经OVA多肽刺激后, 在不同的Th17极化的培养条件下, 观察Th17细胞及细胞因子的产生. 结果: 单纯OVA抗原刺激主要诱导特异性Th1型反应, 在TGF-β和IL-6存在的条件下, 主要诱导Th17反应; 当加入IL-23之后, 促进了Th17细胞的分化.阻断了IFN-γ和IL-4之后, Th17细胞的百分率明显增加.LPS可以促进Th1型细胞因子的产生, 但对抗原特异性Th17细胞的分化没有明显的促进作用.结论: 抗原特异性Th17细胞是与Th1、 Th2相对独立的细胞亚群, TGF-β、 IL-6和 IL-23可诱导或促进Th17的分化, 而Th1和Th2细胞因子抑制其分化.     

Complementary role of CD4+CD25+ regulatory T cells and TGF-beta in oral tolerance

CD4(+)CD25(+) regulatory T cells are thought to be generated in the periphery as well as in the thymus. We sought to determine the roles played by CD4(+)CD25(+) T cells and transforming growth factor-beta (TGF-beta) in the induction and maintenance of tolerance generated by oral antigens in BALB/c mice. We found that oral administration of a high dose of ovalbumin (OVA) suppressed OVA-specific proliferation and antibody production in BALB/c mice depleted of CD25(+) cells. In contrast, the unresponsiveness induced by lower doses of OVA was only partially blocked by CD25 depletion prior to feeding. Depletion of CD4(+)CD25(+) cells after mice were orally tolerized did not reverse the tolerant status, indicating that these cells were not required to maintain the established tolerance. Furthermore, the induction of oral tolerance was not hampered by the administration of TGF-beta-neutralizing antibodies. However, in mice depleted of CD25(+) cells, anti-TGF-beta-neutralizing antibodies blocked the induction of tolerance, regardless of whether the mice followed the high- or low-dose regimens of oral OVA. CD25 depletion together with TGF-beta neutralization led the expansion of OVA-specific CD4 T cells against the subsequent antigen challenge, and each treatment alone did not. Our findings indicate that CD4(+)CD25(+) T cells and TGF-beta play a complementary role in the induction of oral tolerance, at least in part, by regulating the expansion of antigen-specific CD4 T cells.     

An obligate role for T-cell receptor alphabeta+ T cells but not T-cell receptor gammadelta+ T cells, B cells, or CD40/CD40L interactions in a mouse model of atopic dermatitis

BACKGROUND: We recently described a murine model of atopic dermatitis (AD) elicited by epicutaneous sensitization with ovalbumin (OVA). The skin lesions in these mice were characterized by a dermal infiltrate consisting of eosinophils and T cells and by increased expression of the TH2 cytokines IL-4 and IL-5. Epicutaneous sensitization induces a rise in the levels of serum total IgE and OVA-specific antibodies, further indicating that it elicits a predominantly TH2 response. OBJECTIVE: This study was undertaken to assess the roles of T cells, B cells, and CD40L-CD40 interactions in AD. METHODS: Mice with targeted gene deletions were sensitized with OVA. Histologic and immunohistochemical examinations, as well as measurements of IL-4 mRNA, were performed on OVA-sensitized skin. Total and antigen-specific serum IgE levels were determined. RESULTS: RAG2(-/-) mice, which lack both T and B cells, did not exhibit cellular infiltration, induction of dermal IL-4 mRNA, or elevation of serum IgE after OVA sensitization; all of these features were present in B-cell-deficient IgH(-/-) mice. T-cell receptor alpha(-/-) mice did not display cellular infiltration, IL-4 mRNA expression, or increased IgE levels after OVA sensitization, but these responses were elicited in T-cell receptor delta(-/-) mice after sensitization. Absence of CD40 had no effect on these responses. CONCLUSION: These results suggest that alphabeta T cells, but not gammadelta T cells, B cells, or CD40L-CD40 interactions, are critical for skin inflammation and the TH2 response in AD.     

IgE enhances specific antibody and T-cell responses in mice overexpressing CD23

Abstract IgE administered with its specific antigen in vivo induces enhanced proliferation of specific T cells as well as enhanced production of specific antibodies. Both effects are dependent on the low-affinity receptor for IgE (CD23) and the underlying mechanism is thought to be increased antigen presentation following uptake of IgE/antigen complexes via CD23⁺ B cells. By contrast, CD23 negatively regulates antibody responses to antigens administered with alum, i.e. without IgE. This effect has been observed as low IgG1 and IgE responses in transgenic mice overexpressing CD23 (CD23Tg). The present study was designed to test whether IgE could enhance antibody and T-cell responses in CD23Tg animals or whether CD23's downregulatory effect precludes IgE-mediated enhancement. IgE-anti-TNP administered with OVA-TNP enhances the OVA-specific antibody responses in wild-type (wt) and CD23Tg mice equally well. Interestingly, the total magnitude of antibody responses to IgE + OVA-TNP and to uncomplexed OVA-TNP, as well as to sheep erythrocytes and keyhole limpet haemocyanine, were lower in the CD23Tg mice. IgE induced proliferation of OVA-specific CD4⁺ T cells to the same degree in wt and CD23Tg mice. The effect on T cells was dependent on CD23⁺ B cells as demonstrated in in vitro proliferation assays. In conclusion, CD23 does indeed have dual immunoregulatory effects in the same animal. The receptor mediates enhancement of antibody and T-cell responses to IgE-complexed antigen, most likely via increased presentation of complexed antigen, while it negatively regulates the total antibody response to a variety of antigens.     

Oral antigen induces antigen-specific activation of intraepithelial CD4+ lymphocytes but suppresses their activation in spleen

Intraepithelial lymphocytes (IELs) are considered to drive immune surveillance of the epithelial layer to the mucosa, which is initially exposed to exogenous antigens. However, how IELs are activated by orally administered antigens remains unclear. To clarify this mechanism, we fed ovalbumin (OVA) to T cell receptor transgenic (TCR-Tg) mice with OVA-specific MHC class II-restricted TCR and found that the cytotoxic activity of IELs was increased against both NK and LAK target cells, but notably reduced after depleting CD8 + IELs. Cytoplasmic staining showed that the production of IFN-gamma and IL-2 was increased in mice fed with OVA both in the supernatant of cultured IELs with immobilized anti-CD3 mAb and in fresh CD4+ IELs. In contrast, the cytotoxic activity against NK and LAK target cells and the production of IL-2 and IFN-gamma was decreased in splenic T cells from mice fed with OVA. However, when the splenic T cells from these mice were cultured with OVA and IL-2, IFN-gamma production recovered. The decreased response demonstrated the clonal anergy of T cells. Furthermore, tumor growth was enhanced in TCR-Tg mice carrying an OVA-transfected counterpart A20 B cell lymphoma (OVA-A20) and fed with OVA. These results indicate that the oral administration of soluble antigens can activate CD4+ IELs in an antigen-specific manner but induces hyporesponsiveness in the spleen. In addition, Th1-type cytokines produced by activated CD4+ IEL might provide a bystander effect on the cytotoxic activity of IELs.     

IgE-dependent enhancement of Th2 cell-mediated allergic inflammation in the airways

T helper 2 (Th2) cell-derived cytokines, including interleukin (IL)-4, IL-5 and IL-13, play important roles in causing allergic airway inflammation. In contrast to Th2 cells, however, the role of IgE and mast cells in inducing allergic airway inflammation is not understood fully. In the present study, we addressed this point using transgenic mice expressing trinitrophenyl (TNP)-specific IgE (TNP-IgE mice), which enable us to investigate the role of IgE without the influence of antigen-specific T cell activation and other immunoglobulins. When the corresponding antigen, TNP-BSA, was administered intranasally to TNP-IgE mice, a large number of CD4+ T cells were recruited into the airways. In contrast, TNP-BSA administration did not induce eosinophil recruitment into the airways or airway hyperreactivity. Furthermore, when ovalbumin (OVA)-specific Th2 cells were transferred to TNP-IgE mice and the mice were challenged with inhaled OVA, TNP-BSA administration increased OVA-specific T cell recruitment and then enhanced Th2 cell-mediated eosinophil recruitment into the airways. These results indicate that IgE-induced mast cell activation principally induces CD4+ T cell recruitment into the airways and thus plays an important role in enhancing Th2 cell-mediated eosinophilic airway inflammation by recruiting Th2 cells into the site of allergic inflammation.