Resting B cells can act as antigen presenting cells in vivo and induce antibody responses

Although it is well established that B lymphocytes are ableto present antigen in vitro, the ability of small resting Bcells to act as antigen presenting cells in vivo remains controversial.In this report we have studied the antigen presentation andthe antibody response induced by mouse B cells after in vivoor in vitro targeting antigens to membrane Ig (mIg), using ratmAbs. Our results show that injection of these mAbs coupledto 2,4-dinitrophenyl (DNP) strongly enhances the IgG1 antibodyresponse against DNP and rat Ig. T cell depleted spleen cellspulsedin vitro with rat Ig without specificity for B cells inducedan antibody response when re-injected into mice, this responsebeing much higher if the antigen was specific for mlg. Moreover,purified resting B cells were shown to induce a specific IgG1response in vivo only when they were cultured with rat mAb againstmIgM or mIgD but not with myeloma rat Ig of the same isotype.B cells do not need to be activated to present antigen sincethe induction of the specific antibody response does not correlatewith the mitogenic activity of rat mAb nor with the IgG1 polyclonalsynthesis in vivo. These data clearly show that resting B cellscan present antigen in vivo and induce an antibody response,and underline the importance of mIgM and mIgD as targets forantigens.     

Specific antigen/antibody complexes induce the in vivo production of a parallel set of nonantigen-binding idiotype-positive antibodies

Immune complexes prepared with the polysaccharide antigen (PnC) extracted from Streptococcus pneumoniae R36a and two different PnC-specific antibodies were found to differ in their regulatory properties depending on the isotype of the antibody. Thus, complexes formed in antibody excess with TEPC15 (IgA) were suppressive whereas complexes formed with 96-G (IgG3) antibodies enhanced the IgM response to PnC. During the course of these studies, we found that little or no PnC-specific IgG antibody was induced during the response to PnC coupled to sheep red blood cells (PnC-SRBC). Interestingly, however, immunization with 96-G/PnC complexes either alone or with PnC-SRBC resulted in the induction of IgG3 antibodies that express the T15 idiotype (Id) but which do not bind PnC. This unique IgG3 response occurred after injection of 96-G/PnC complexes formed in antibody excess but not when complexes were formed in antigen excess. The Id+ nonspecific IgG3 response peaked on day 5 and could be activated with 96-G/PnC complexes but not with free PnC antigen. The Id+ nonspecific response was not due to polyclonal activation of IgG3 production since there was no difference in IgG3 levels in mice injected with 96-G/PnC complexes with those injected with PnC-SRBC. Finally, mice that had been suppressed for expression of the T15 Id by neonatal injection of anti-Id antibody were able to produce Id+-unspecific IgG3 antibody after immunization with 96-G/PnC complexes, further suggesting that Id+ IgG3 was produced by different clones than those that usually comprise the antibody response to PnC. The results suggest that the formation of IgG immune complexes during an immune response may result in stimulation of idiotypically related clones thus resulting in degeneracy of the immune response.     

乙型肝炎病毒抗原表位模拟多肽诱导CTL应答的研究

目的 应用分子设计技术设计治疗性多肽，以探讨基于乙型肝炎病毒(Hepatitis B virus，HBV)核心抗原优势细胞毒性T淋巴细胞(Cytotoxic T lymphocyts，CTL)表位的多肽设计与启动HLA-I限制性HBV特异性CD8^ T细胞应答的关系。方法 合成含HBcAg免疫优势CTL表位、Pre-S2蛋白优势B细胞表位和破伤风类毒素通用TH表位的多肽，并进行HLA-A2^ 人—PBMC体外和Balb／c小鼠体内免疫学功能研究。结果 上述多肽可在体内外诱导CD8^ CTL应答。以棕榈酸为分子内佐剂的Palm-p44可诱导较强的CD8^ CTL应答，与单纯多肽比较不需另加佐剂。结论 脂类分子内佐剂可显著提高多肽的免疫原性；Palm-p44可作为乙型肝炎治疗性多肽疫苗设计较有效的候选分子。     

Medroxyprogesterone acetate enhances in vivo and in vitro antibody production

In the present study we examine the effects of medroxyprogesterone acetate (MPA) on the specific antibody secretion to T-dependent antigens. Our results show that the in vivo administration of MPA to mice, 7 or 90 days before immunization with sheep red blood cells (SRBC), significantly enhanced both, primary and secondary antibody responses, without affecting delayed-type hypersensitivity (DTH). These effects could be counteracted by the anti-progestin onapristone or ZK 98299 (ZK) suggesting that MPA interacted with progesterone (PRG) receptors to increase B-cell response. To better understand the mechanisms involved in MPA activity we carried out cultures of splenocytes, bone marrow cells or lymph node cells from immunized mice in the presence of MPA, and evaluated the amount of antibody release to supernatants. We found that low doses of MPA (10(-9) M and 10(-10) M) significantly enhanced the in vitro production of specific immunoglobulin G (IgG) antibodies, an effect that appears to involve the interaction of the progestin with PRG receptors, as judged by the inhibition of MPA effects with ZK (10(-8) M) or RU486 (10(-9) M). These receptors were detected by flow cytometry analysis in a proportion of T lymphocytes. Because MPA did not increase the number of immunoglobulin-secreting cells, our findings suggest that MPA enhanced the capacity of individual cells to produce specific immunoglobulin.     

Suppression of IgA antibody production by in vivo complement depletion

The thymus-dependent IgA and IgG antibody responses to parenteral immunization of mice with sheep erythrocytes were suppressed by injection of cobra factor, the C3-activating protein of Naja naja venom. The less thymus-dependent IgM component of the response was only slightly impaired. These observations extend to IgA antibody production evidence that complement participates in the induction of immunological responses based on T–B lymphocyte co-operation.     

In vivo CD40 ligation can induce T-cell-independent antitumor effects that involve macrophages

We have previously demonstrated T cell-independent antitumor and antimetastatic effects of CD40 ligation that involved natural killer (NK) cells. As CD40 molecules are expressed on the surface of macrophages (Mphi), we hypothesized that Mphi may also serve as antitumor effector cells when activated by CD40 ligation. Progression of subcutaneous NXS2 murine neuroblastomas was delayed significantly by agonistic CD40 monoclonal antibody (anti-CD40 mAb) therapy in immunocompetent A/J mice, as well as in T and B cell-deficient severe combined immunodeficiency (SCID) mice. Although NK cells can be activated by anti-CD40 mAb, anti-CD40 mAb treatment also induced a significant antitumor effect in SCID/beige mice in the absence of T and NK effector cells, even when noncytolytic NK cells and polymorphonuclear cells (PMN) were depleted. Furthermore, in vivo treatment with anti-CD40 mAb resulted in enhanced expression of cytokines and cell surface activation markers, as well as Mphi-mediated tumor inhibition in A/J mice, C57BL/6 mice, and SCID/beige mice, as measured in vitro. A role for Mphi was shown by reduction in the antitumor effect of anti-CD40 mAb when Mphi functions were inhibited in vivo by silica. In addition, activation of peritoneal Mphi by anti-CD40 mAb resulted in survival benefits in mice bearing intraperitoneal tumors. Taken together, our results show that anti-CD40 mAb immunotherapy of mice can inhibit tumor growth in the absence of T cells, NK cells, and PMN through the involvement of activated Mphi.     

Liposomal microparticle injection can induce myeloid-derived suppressor cells (MDSC)-like cells in vivo

Context: Myeloid-derived suppressor cells (MDSCs) are a subset of immature myeloid cells that function as immunosuppressive cells in various pathological conditions. Membrane-derived microvesicles are thought to be involved in MDSC induction. Earlier reports have described that injection of considerable amount of liposome into rat can suppress Con A-induced splenic T-cell proliferation. Liposome-internalized cells expressing CD11b/c suppress T-cell proliferation. Nitric oxide (NO) appears to be involved in the suppression. We speculated that, similarly to membrane-derived microvesicles, liposomal microparticles can induce MDSC-like cells in vivo.

Objectives: To confirm our speculation we investigated dose-dependency of the suppressive effect, the effect of liposome on the induction of inducible NO synthase (iNOS), and anti-CD3 antibody-stimulated T-cell proliferation and cytokine production.

Materials and methods: Liposome particles of 250?nm diameter were prepared and suspended in saline. Then, various amounts of liposomal suspension were injected intravenously into rats. After 24?h, rat spleens were removed and concanavalin A (or anti-CD3 antibody) stimulated-splenic T-cell proliferation and the production of iNOS, NO and cytokines were evaluated.

Results: T-cell proliferation was suppressed dose-dependently by liposome injection. The immunosuppressive cell exerts its suppressive activity in a dose-dependent manner. The suppression was eliminated by iNOS inhibitor. iNOS was detected in liposome-loaded splenocytes. Anti-CD3 antibody-stimulated T-cell proliferation was also inhibited. Enhanced production of IL-10 was observed.

Conclusions: Liposomal microparticles can induce MDSC-like cells in vivo. The lipids which comprise liposomes might serve an important role in the induction of MDSCs in vivo.     

In vivo alteration of antibody production in patients with IgA nephropathy

Augmentation of IgA production has been postulated for the development of IgA nephropathy. An influenza HA vaccine was administered to healthy adults and patients with IgA nephropathy to elucidate if there was any in vivo alteration of antibody production in response to antigenic stimulation in these patients. The vaccine was administered s.c. in a dose of 350 CCA units at an interval of 4 weeks. IgG, IgA and IgM class antibodies to influenza HA antigens and three classes of rheumatoid factors (RF) were determined using a solid phase fluorescence immunoassay. The titres of IgG class antibodies to influenza HA antigens did not change significantly in either group after the vaccination. No significant differences were observed in the titres of IgG antibodies between the two groups. IgA antibodies were significantly increased only in patients in the 4th week and continued to the 8th week. The titres of IgA antibodies were always higher in patients than in controls during the study period. IgM antibodies were significantly increased stepwise in both groups to an equal degree. IgG and IgA RF were always higher in patients than in controls. IgM RF were significantly increased and higher than in controls in the 8th week in patients. It is concluded that patients with IgA nephropathy might be high responders for IgA antibody production, and that polyclonal activation might be associated with increased IgA production following in vivo antigenic stimulation in these patients.     

Down-regulation of antigen-specific antibody production by TCR antagonist peptides in vivo

The efficacy of TCR antagonist peptides in inhibition of antigen-specific antibody production and T cell responses in vivo was evaluated. Among amino acid-substituted analogs of a peptide corresponding to residues 119 - 133 of bovine beta-lactoglobulin (p119 - 133), pR124Q and pD129S, prepared by substitution of Gln and Ser for Arg(124) and Asp(129), respectively, have been shown to display TCR antagonist activity for three out of four distinct p119 - 133-specific T cell clones and for polyclonal T cells derived from p119 - 133-immunized C57BL / 6 mice. Both pD129S and pR124Q inhibited in vivo priming and subsequent activation of T cells by p119 - 133 when co-injected with p119 - 133 into mice, as shown by the decreased proliferation of T cells in response to p119-133 in vitro. pD129S significantly inhibited production of anti-p119 - 113 antibodies of IgG1, IgG2b and IgE isotype in vivo when co-injected into mice together with p119 - 133 at the time of the first immunization. However, pR124Q was totally ineffective in inhibition of the antibody responses. Anti-p119 - 133 antibodies from p119 - 133-immunized mice could bind to pR124Q but not to pD129S, suggesting that the difference in cross-reactivity is responsible for the different effect of these two peptides on specific antibody production. Our findings demonstrate that a single TCR antagonist peptide can inhibit antigen-specific polyclonal antibody production when this antagonist peptide does not cross-react with the antibody elicited in response to an antigenic peptide.