The development of IgE+ memory B cells following primary IgE immune responses

We studied whether long-lived IgE⁺ memory B cells develop following three types of primary IgE immune responses. Immunization of mice with anti-IgD antibody induced a T cell-dependent, interleukin (IL)-4-dependent primary IgE response and the formation of IgE isotype switched (IgE⁺) memory B cells. These IgE⁺ memory B cells could be stimulated in vivo by injection with goat anti-IgE antibodies to produce a profound IL-4-independent memory IgE response. By contrast, both infection of mice with Nippostrongylus brasiliensis or repeated immunization with benzylpenicilloyl-keyhole limpet hemocyanin (BPO-KLH) in alum stimulated good primary IgE responses and profound memory T cell-dependent antigen-specific IgE responses, but failed to induce the development of long lived IgE⁺ memory B cells because they could not be recalled with goat anti-IgE antibodies. Mice receiving double immunizations combining anti-IgD with either N. brasiliensis infection or BPO-KLH immunization mounted significant goat anti-IgE-induced secondary IgE responses, but no N. brasiliensis or BPO-KLH-specific IgE could be detected. This indicates that the N. brasiliensis and BPO-KLH induced immune responses do not suppress the development of IgE⁺ B cells, but rather, do not provide the necessary conditions for their formation. Taken together these data indicate that long-lived IgE⁺ B cells fail to develop during the primary IgE response to N. brasiliensis infection or BPO-KLH immunization. By contrast, significant numbers of IgE⁺ memory B cells form during the primary IgE immune response induced by anti-IgD immunization. Our observations suggest that immunization protocols involving membrane IgD cross-linking and limited duration of cognate T cell help are necessary for the formation of IgE⁺ memory B cells. It will be important to determine the relevance of membrane IgD interaction with allergens, as this would influence the design of new therapies for the treatment of allergy and asthma.     

Antigen-specific CD8+ T cells inhibit IgE responses and interleukin-4 production by CD4+ T cells

There is a growing body of evidence which suggests that CD8⁺ T cells play an important part in regulating the IgE response to non-replicating antigens. In this study we have systematically investigated their role in the regulation of IgE and of CD4⁺ T cell responses to ovalbumin (OVA) by CD8⁺ T cell depletion in vivo. Following intraperitoneal immunization with alum-precipitated OVA, OVA-specific T cell responses were detected in the spleen and depletion of CD8⁺ T cells in vitro significantly enhanced the proliferative response to OVA. Depletion of CD8⁺ T cells in vivo 7 days after immunization failed to enhance IgE production, while depletion of CD8⁺ T cells on days 12–18 greatly enhanced the IgE response, which rose to 26 μ/ml following a second injection of anti-CD8 on day 35 and remained in excess of 1 μ/ml over 300 days afterwards. Reconstitution on day 21 of rats CD8-depleted on day 12 with purified CD8⁺ T cells from animals immunized on day 12 completely inhib ited the IgE response. This effect was antigen specific; CD8⁺ T cells from OVA-primed animals had little effect on the IgE response of bovine serum albumin immunized rats. In vivo, CD8⁺ T cell depletion decreased interferon (IFN)-γ production but enhanced interleukin (IL)-4 production by OVA-stimulated splenic CD4⁺ T cells. Furthermore, CD8⁺ T cell depletion and addition of anti-IFN-γ antibody enhanced IgE production in vitro in an IL-4-supplemented mixed lymphocyte reaction. These data clearly show that antigen-specific CD8⁺ T cells inhibit IgE in the immune response to non-replicating antigens. The data indicate two possible mechanisms: first, CD8⁺ T cells have direct inhibitory effects on switching to IgE in B cells and second, they inhibit OVA-specific IL-4 production but enhance IFN-γ production by CD4⁺ T cells.     

Inhibition of Antigen-Specific IgE Production by Antigen Coupled to Membrane IgE Peptide

The membrane IgE peptide (MEP) encompassing 20 amino acids proximal to the C terminus of membrane IgE molecules, and secretory IgE peptides (SEP), spanning CHε 1 to 4 domain were synthesized according to IgE genomic and cDNA sequences. Inhibition of anti-KLH and anti- BGG IgE, but not IgG responses was observed in mice treated with MEP-protein but not SEP- protein conjugates in complete/incomplete Freund's adjuvant. Only IgE responses directed toward proteins to which MEP was conjugated, were inhibited, while IgE responses to a concomitantly injected, unrelated antigen were not. Inhibition of antigen-specific IgE was also not correlated with levels of anti-MEP or anti-IgE antibodies; moreover, levels of total IgE remained comparable among mice treated with MEP-protein conjugates, native or glutaraldehyde-modified protein carriers. This observation may have significant import on future design of IgE immunotherapy. Treatment of MEP conjugated allergens prevents formation of IgE-anti-IgE complexes because the MEP sequence is absent from the secretory IgE.     

T cell epitopes of Per a 10 modulate local-systemic immune responses and airway inflammation by augmenting Th1 and T regulatory cell functions in murine model

Peptide immunotherapy (PIT) represents a safe and efficacious therapeutic modality for allergic diseases. Present study evaluates immunotherapeutic potential of T cell peptides of major cockroach allergen, Per a 10 in murine model of airway allergy. Treatment with peptides T-P8 and T-P10 demonstrated maximal resolution of pathophysiological features such as reduced recruitment of inflammatory cells to airways, lowered specific IgE, induction of IgG2a antibodies in serum, immune deviation towards Th1 cytokine milieu, suppression of Th2 cytokines in BALF and splenocyte culture supernatant and resolution of lung inflammation. A significant increase in CD4⁺Foxp3⁺ cells in spleen indicate towards induction of T regulatory cell mediated peripheral tolerance characterized by shift in cytokine milieu from Th2 to T regulatory cytokines. PIT modulates regulation of immune responses at both local and systemic levels, contributes towards holistic improvement in allergic features in mice and thus demonstrate potential for safe, specific and efficacious treatment for cockroach allergy.     

Genesis of host IgE competence: perinatal IgE tolerance induced by IgE processed and presented by IgE Fc receptor (CD23)-bearing B cells.

A murine model for studying life-long IgE tolerance was previously developed in this laboratory by perinatal IgE injection into neonates. Herein, we demonstrated that normal and immortal CD23+ B cell lines presented processed IgE via CD23-mediated endocytic pathway and triggered perinatal IgE tolerance. The observations were as followed: (a) CD23 on normal B cells or B cell hybridomas mediated IgE-dependent perinatal IgE tolerance and total IgE deficiency; and lack of either antigen-specific IgE or total IgE did not correlate with elevated levels of autologous anti-IgE in individual mice; (b) IgE tolerance-inducing capacity of CD23+ B cell hybridomas was augmented by treatment with antigen-IgE complexes or interleukin 4, and significantly inhibited by anti-CD23 prior to IgE pulsing; (c) antigen-IgE complexes were endocytosed and degraded in acid hydrolases-containing vesicles; and IgE tolerance was abrogated by treating IgE-pulsed 17A11 at 4 degrees C or 20 degrees C followed immediately by fixation, and by treating IgE-pulsed 17A11 with metabolic inhibitors that elevated intracellular pH of the endocytic vesicles. In conclusion, this study suggested that one pivotal step of genetic control of IgE responses may be exercised at the early developmental stage of T cells of the IgE lineage, and that CD23 may facilitate capture of endogenously secreted IgE, and mediate endocytic processing and presentation of self IgE epitope(s), and thus contribute to the genesis of host IgE competence.     

Antigen dose‐dependent suppression of murine IgE responses is mediated by CD4−CD8− double‐negative T cells

Background The IgE response against protein antigens is profoundly influenced by the dose used for sensitization. Objective The aim of the study was to identify immune cells that are involved in antigen dose‐dependent regulation of IgE formation. Methods Wild‐type mice as well as T helper (Th)1‐deficient IL‐12p40^?/? and IFN‐γ^?/? mice were immunized by repeated intraperitoneal injection of either low doses (K01 mice) or high doses (K100 mice) of keyhole limpet haemocyanin adsorbed to aluminium hydroxide. Splenocytes of immunized mice were restimulated in vitro and antigen‐dependent T cell proliferation and cytokine production were measured. The frequency of regulatory T cell subsets among splenocytes from K01 and K100 mice was compared using fluorocytometry and RT‐PCR analysis. Splenocytes or T cell subpopulations were transferred into naïve mice and the effect of lymphocyte transfer on IgE production after priming of recipients with low antigen doses was determined. Results Specific IgE production was considerably impaired in K100 mice. Antigenic restimulation revealed hypoproliferation of K100 splenocytes and reduced production of Th2 cytokines IL‐4, IL‐5 and IL‐13, but no induction of IFN‐γ production. Moreover, lymphocytes from K01 and K100 mice did not show significant differences in the expression of molecules associated with the phenotype or activity of conventional regulatory T cells. Transfer of splenocytes or purified T cells from K100 mice substantially suppressed the induction of IgE production in the recipients in an antigen‐ and isotype‐specific manner. Neither CD4⁺ nor CD8⁺ T cells from K100 mice were able to inhibit IgE formation; instead, we identified CD4^?CD8^? double‐negative T cells (dnT cells) as the principal T cell population, which potently suppressed IgE production. Conclusion Our data demonstrate that CD4^?CD8^? dnT cells play a major role in the regulation of IgE responses induced by high antigen doses.     

B7-H1 on myeloid-derived suppressor cells in immune suppression by a mouse model of ovarian cancer

Myeloid-derived suppressor cells (MDSCs) accumulate in tumor-bearing hosts and are associated with immune suppression. Here, we described high level of expression of B7-H1 (CD274), PD-1 (CD279) and CTLA4 (CD152) by Gr-1⁺CD11b⁺ MDSCs obtained from both ascites and spleens of mice bearing the 1D8 ovarian carcinoma, whereas B7-DC (CD273), CD40 and CD86 were absent. In contrast, B7-H1, PD-1 and CTLA-4 expression was not detected on Gr-1⁺CD11b⁺ cells from naive mice. Expression of B7-H1 by Gr-1⁺CD11b⁺ cells from naive mice could be induced by co-culture with 1D8 ovarian carcinoma cells. Gr-1⁺CD11b⁺ cells derived from 1D8 tumor-bearing mice markedly suppressed antigen-specific immune responses, whereas Gr-1⁺CD11b⁺ cells from naive mice did not. siRNA-mediated knockdown of B7-H1 in Gr-1⁺CD11b⁺ cells of 1D8 tumor-bearing mice alleviated suppression of antigen-specific immune responses. Suppression of antigen-specific immune responses via B7-H1 on Gr-1⁺CD11b⁺ myeloid cells was mediated by CD4⁺CD25⁺ Foxp3⁺ T regulatory cells and required PD-1. Antibody blockade of either B7-H1 or PD-1 retarded the growth of 1D8 tumor in mice. This suggests that expression of B7-H1 on Gr-1⁺CD11b⁺ myeloid cells triggered by the 1D8 mouse model of ovarian carcinoma suppresses antigen-specific immunity via interaction with PD-1 on CD4⁺CD25⁺ Foxp3⁺ regulatory T cells.     

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.     

The relative contribution of IL-4 and IL-13 to human IgE synthesis induced by activated CD4 or CD8 T cells

The relative contribution of IL-4 and IL-13 to the regulation of IgE synthesis has remained relatively poorly characterized, partially because of lack of suitable animal models. We have studied the roles of IL-4 and IL-13 in human IgE synthesis induced by supernatants derived from activated CD4⁺⁺ or CD8⁺ T cell clones. Neutralizing anti–IL-4 and anti–IL-13 monoclonal antibodies (mAbs) inhibited IgE synthesis induced by anti-CD40 mAbs and supernatants from CD4⁺ T cells by an average 61% and 42%, respectively (n = 25). Recombinant IL-13 had additive effects on IL-4-induced IgE synthesis, but only when IL-4 was present at low concentrations. Accordingly, IL-4 was the dominant IgE synthesis–inducing cytokine derived from highly polarized T helper (TH)₂ cells. However, anti–IL-13 mAbs also significantly inhibited IgE synthesis induced by two of three supernatants derived from allergen-specific T_H2-like cell lines generated from the skin of patients with atopic dermatitis. Furthermore, anti–IL-13 mAbs almost completely inhibited IgE synthesis induced by supernatants from T_H1 cells or CD8⁺ T cell clones. Taken together, these data indicate that IL-13, in addition to IL-4, contributes to IgE synthesis induced by all T helper cell subsets, including allergen-specific T_H2 cells. Moreover, IL-13 appears to be the major IgE synthesis–inducing cytokine derived from T_H1 cells or CD8⁺ T cells. (J Allergy Clin Immunol 1997;100:792-801.)     

Secondary but not primary T cell responses are enhanced in CTLA-4-deficient CD8+ T cells

Negative as well as positive co-stimulation appears to play an important role in controlling T cell activation. CTLA-4 has been proposed to negatively regulate T cell responses. CTLA-4-deficient mice develop a lymphoproliferative disorder, initiated by the activation and expansion of CD4⁺ T cells. To assess the function of CTLA-4 on CD8⁺ T cells, CTLA-4^−/- animals were crossed to an MHC class I-restricted 2C TCR transgenic mouse line. We demonstrate that although the primary T cell responses were similar, the CTLA-4-deficient 2C TCR⁺ CD8⁺ T cells displayed a greater proliferative response upon secondary stimulation than the 2C TCR⁺ CD8⁺ T cells from CTLA-4 wild-type mice. These results suggest that CTLA-4 regulates antigen-specific memory CD8⁺ T cell responses.     

Specific T cell lines for ovalbumin, ovomucoid, lysozyme and two OA synthetic epitopes, generated from egg allergic patients' PBMC

Background Proteitis of hen egg white are common ingredients of food and difficult to eliminate. Allergens of egg while induce allergic symptoms among relatively high numbers of palients suffering from food allergy. B cell epitopes to hen egg white tnajor allergens have been reported. Considering that IgE antibody formation is mostly T cell dependent, the study of T cell epitopes is essential for both T cell dependent and independent IgE response. Objectives Little information on T cell epitopes recognizing food allergens has been reported. T cell responses to hen egg white allergens and two synthetic OA peptides located at amino acid residues No. 105–122 and 323–339 were investigated. Methods Peripheral blood mononuclear cells from hen egg allergic patients were investigated. Various allergens of hen egg white were used for stimulation. Primary proliferation responses were detected followed by the generation of long-term cultures which were examined for their specificity, phenotype, cytokine profile and IgE production. The allergen specific T cell lines were mapped using a panel of 13 synthetic peptides of ovalbumin. Results Human T cells recognizing ovomucoid, lysozyme and ovalbumin epitope 105–122 are reported for the first time. The cell lines were enriched CD4⁺/CD8⁺ T cells (CD2⁺ 95%). Ovomucoid and ovalbumin induced IgE synthesis by a small fraction of B cells (1%) present in the ovalbumin and ovomucoid specific T cell lines. Conclusions Human T cells recognized several egg white allergens and epitopes within the ovalbumin molecule. Specific IgE was produced in cultures stimulated with ovalbumin and ovomucoid. OA peptides 105–122 and 323–339 have no affinity to the specific IgE of the two patients; an observation which could be of particular interest regarding the mechanisms of peptide-based immunotherapy.     

Prolonged In Vivo IL-4 Treatment Inhibits Antigen-Specific IgG1 and IgE Formation

IL-4 is obligatory for primary IgE responses, whereas primary IgG, and secondary IgE responses are partially IL-4 independent. To investigate the effect of IL-4 on the antigen-specific memory formation for these isotypes, BALB/c mice were treated after primary TNP-KLH immunization with recombinant IL-4 for a period of 4 months. This prolonged presence of a high IL-4 level resulted in increased serum levels of total IgG₁ and IgE, whereas total IgG_2a did not change. The expression of CD23, but not J-A^d, increased on the splenic B cells. IL-4 treatment did not affect the IL-4 production by Con A stimulated spleen cells, whereas it did decrease the IFN-γ production. In the same mice the TNP-specific IgG₁ and IgE serum levels, however, were decreased. Similar results were found when the antigen was continuously present during the IL-4 treatment. Furthermore, it was shown that IL-4 decreased the formation of IgG₁, and IgE memory cells. These results point to different effects of IL-4 in regulating antigen-specific and bystander responses.     

T helper cell IL-4 drives intestinal Th2 priming to oral peanut antigen,under the control of OX40L and independent of innate-like lymphocytes

Intestinal T helper type 2 (Th2) immunity in food allergy results in IgG1 and IgE production, and antigen re-exposure elicits responses such as anaphylaxis and eosinophilic inflammation. Although interleukin-4 (IL-4) is critically required for allergic sensitization, the source and control of IL-4 during the initiation of Th2 immunity in vivo remains unclear. Non-intestinal and non-food allergy systems have suggested that natural killer-like T (NKT) or γδ T-cell innate lymphocytes can supply the IL-4 required to induce Th2 polarization. Group 2 innate lymphoid cells (ILCs) are a novel IL-4-competent population, but their contribution to initiating adaptive Th2 immunity is unclear. There are also reports of IL-4-independent Th2 responses. Here, we show that IL-4-dependent peanut allergic Th2 responses are completely intact in NKT-deficient, γδ T-deficient or ILC-deficient mice, including antigen-specific IgG1/IgE production, anaphylaxis, and cytokine production. Instead, IL-4 solely from CD4⁺ Th cells induces full Th2 immunity. Further, CD4⁺ Th cell production of IL-4 in vivo is dependent on OX40L, a costimulatory molecule on dendritic cells (DCs) required for intestinal allergic priming. However, both Th2 cells and ILCs orchestrated IL-13-dependent eosinophilic inflammation. Thus, intestinal Th2 priming is initiated by an autocrine/paracrine acting CD4⁺ Th cell-intrinsic IL-4 program that is controlled by DC OX40L, and not by NKT, γδ T, or ILC cells.     

The effect of disodium cromoglycate (DSCG) on in vitro proliferation of CD4+, CD8+, and CD19+ cell populations derived from allergic and healthy donors

The effect of disodium cromoglycate (DSCG) on in vitro proliferation of CD4⁺ and CD8⁺ T cells and CD19⁺ B cells, positively selected by immunomagnetic separation, was investigated. The cells were obtained from allergic patients with moderate serum IgE levels and mild to moderate atopic dermatitis, and healthy controls. The different cell subfractions were stimulated with mitogens or specific allergens, as well as cell supernatants from the lymphoblastoid B- (RPMI 8866) and T-hybridoma (166 A₂) cell lines. Proliferative responses of T- and B-cell subsets stimulated with mitogens together with recombinant interleukin-2 (rIL-2) or accessory cells (AC) could be inhibited by DSCG. In allergic individuals, significant allergen-specific stimulation could be observed in the CD8-depleted peripheral blood mononuclear cell (PBMC) fractions. Isolated CD4⁺ T cells, without AC or IL-2, could also be stimulated with specific allergen, but the responses were rather low. DSCG inhibited, concentration dependently, all allergen-induced responses. Interestingly, only atopic derived CD4⁺ and CD8⁺ T cells were stimulated by soluble low-affinity IgE receptor (Fc?RII/sCD23) and IgE binding factor (IgEBF), including IgE enhancing factor, present in culture supernatants from RPMI 8866 and 166 A₂, respectively. These responses were also inhibited by DSCG. This was in contrast to the amplifying effect of DSCG on spontaneously proliferating RPMI 8866 and 166 A₂ cells, cultured in fresh cRPMI 1640 medium without sCD23 and IgE enhancing factor. Our results show that DSCG delivers an inhibitory signal or signals to PBMC subpopulations expressing Fc?RII/sCD23, either upregulated by phytohemagglutinin in normal and atopic cells, or by allergens or sCD23 in atopic cells. The findings suggest that sCD23 in supernatants or in serum may reverse the general inhibitory mode of DSCG.     

The role of antigen-presenting cells and interleukin-12 in the priming of antigen-specific CD4+ T cells by immune stimulating complexes

Immune stimulating complexes (ISCOMs) containing the saponin adjuvant Quil A are vaccine adjuvants that promote a wide range of immune responses in vivo, including delayed-type hypersensitivity (DTH) and the secretion of both T helper 1 (Th1) and Th2 cytokines. However, the antigen-presenting cell (APC) responsible for the induction of these responses has not been characterized. Here we have investigated the role of dendritic cells (DC), macrophages (Mφ) and B cells in the priming of antigen-specific CD4⁺ T cells in vitro by ISCOMs containing ovalbumin (OVA). OVA ISCOMs pulsed bone marrow (BM)-derived DC but not BM Mφ, nor naïve B cells prime resting antigen-specific CD4⁺ T cells, and this response is greatly enhanced if DC are activated with lipopolysaccharide (LPS). Of the APC found in the spleen, only DC had the capacity to prime resting antigen specific CD4⁺ T cells following exposure to OVA ISCOMs in vitro, while Mφ and B cells were ineffective. DC, but not B cells purified from the draining lymph nodes of mice immunized with OVA ISCOMs also primed resting antigen-specific CD4⁺ T cells in vitro, suggesting that DC are also critical in vivo. Using DC and T cells from interleukin (IL)-12 p40^−/− mice, we also identified a crucial role for IL-12 in the priming of optimal CD4⁺ T cell responses by OVA ISCOMs. We suggest that DC are the principal APC responsible for the priming of CD4⁺ T cells by ISCOMs in vivo and that directed targeting of these vectors to DC may enhance their efficancy as vaccine adjuvants.     

A subset of CD8+ T cells from allergic patients produce IL-4 and stimulate IgE production in vitro

Background and Objective A subset of IL-4 producing CD8⁺ T cells was recently identified in HIV patients. Based on these findings we examined whether IL-4 producing CD8⁺ T cells would also be present in allergic patients and what would be the functional relevance of this T-cell population. Methods We investigated the role of CD8⁺ T cells in IgE production of allergic diseases by analysing the cytokine profile of individual CD4⁺ and CD8⁺ T cells. Results In allergic patients about twice as many CD4⁺ T cells and six times as many CD8⁺ T cells produced IL-4 as in non-allergic controls. In contrast the frequency of IFNγ⁺ T-cell subsets did not significantly differ between the allergic and non-allergic individuals. The frequency of 1L4⁺CD8⁺ T cells correlated with the level of serum IgE. Coculture experiments with T cells or purified CD8⁺ T cells together with autologous B cells indicated that CD8⁺ T cells enhanced IgE in vitro, but not IgM production, even when they were physically separated from B cells. This effect could be partially blocked by addition of an IL-4 binding protein, a soluble IL-4 receptor indicating that lL-4 is involved in CD8⁺ T-cell mediated IgE production. Conclusions These data indicate a positive role of IL-4 secreting CD8⁺ T cells in IgE regulation in allergic patients.     

A novel peptide vaccination augments cytotoxic CD8+ T-cell responses against Mycobacterium tuberculosis HspX antigen

Cellular immunity is a critical factor determining the safety and efficacy of newly developed vaccines against Mycobacterium tuberculosis infection. Crosstalk between CD4⁺ and CD8⁺ T-lymphocytes plays central roles in perpetuating the cytotoxic killing to the infected cells for host clearance. Our study proposed a novel alternating MHC-class II restricted peptide vaccination strategy to enhance the antigen-specific CD8⁺ T-cell activity against alpha-crystalline heat-shock protein (HspX) in C57BL/6 mice. Alternating peptide vaccination significantly stimulated a prominent HspX-specific CD8⁺ T-cell response with elevated Th1 and Th17 responses, without interference from Tregs suppression. Heightened central and effector CD8 memory were apparent in mice receiving alternating peptide vaccine, indicating a persisting recall immunity against HspX antigen. It was unlikely for alternating peptide vaccine to cause dysregulation in CD8⁺ T-cells as shown by minimal expression of KLRG1, PD1, LAG3, and CTLA-4 markers. Strong cytotoxic T-lymphocyte (CTL) responses were demonstrated in mice administrated with alternating peptide vaccines, suggesting its capacity in executing killing effector function against targeted cells. In conclusion, our novel vaccination strategy delineated potential benefits of alternating MHC-II peptides to invigorate efficient cytotoxic CD8⁺ T-cell responses against HspX antigen. Such approach might be applicable to serve as alternative immunotherapy for latent tuberculosis infection in future.     

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.     

Immunomodulatory effects of EGCG fraction of green tea extract in innate and adaptive immunity via T regulatory cells in murine model

Green tea is a widely consumed beverage known for its beneficial anti-inflammatory, anti-oxidative, anti-mutagenic, anti-carcinogenic, and cardioprotective properties. Here, we administered epigallocatechin gallate fraction of green tea extract (EGTE) to mice for 6 weeks and examined the effects on the innate and adaptive immune responses by measuring phagocytic and natural killer (NK) cell activity, as well as antigen-specific proliferation, cytolysis, cytokine secretion, and antibody production. Our data show that EGTE administration increased NK cell cytolysis and peritoneal cell phagocytosis, as well as splenocyte proliferation and secretion of IL-2 and IFN-γ. Of note, EGTE treatment decreased the production antigen-specific IgE via increased the proportion of CD4⁺ CD25⁺ regulatory T lymphocytes in the spleen, suggesting that EGTE may play a role in regulating the allergic response.