Developmental immunology最新文献

Since negative selection in the thymus is incomplete, some self-reactive T cells are able to mature and seed the periphery. To study how these T cells interact following encounter with the self-protein they recognize in the periphery, we have developed an adoptive transfer system in which HEL-specific TCR transgenic CD4 T cells are transferred to mice expressing HEL protein in the pancreas under the control of the rat insulin promoter. Here we show that after adoptive transfer of HEL-specific T cells functional tolerance is maintained despite evidence that the T cells encounter and respond to pancreas-expressed antigen. Even the provision of an additional activation stimulus by peripheral immunization with HEL protein is insufficient to induce the T cells to cause autoimmune tissue injury. However, in the presence of blocking anti-CTLA-4-mAb, immunized adoptive transfer recipients rapidly developed diabetes. These data suggest that the CTLA-4 pathway regulates the pathogenicity of antigen-specific T cells following a peripheral activation stimulus.

Epidemiological reports have suggested that the consumption of foods rich in flavonoids is associated with a lower incidence of certain degenerative diseases, including cardiovascular disease. Flavanols and their related oligomers, the procyanidins CFP, isolated from cocoa can modulate the production and level of several signaling molecules associated with immune function and inflammation in vitro, including several cytokines and eicosanoids. To further elucidate the potential immuno-modulatory functions of flavanol-rich cocoa, the present investigation examined whether isolated CFP fractions (monomers through decamers) influence the secretion of tumor necrosis factor-alpha (TNF-alpha) from resting and phytohemagluttinin (PHA)-stimulated human peripheral blood mononuclear cells (PBMC). We used an in vitro culture system where PBMC from 14 healthy subjects were introduced to individual CFP fractions for 72 h prior to measuring the levels of TNF-alpha released. The intermediate-sized CFP fractions (tetramers through octamers) were the most active on resting cells, causing a 3-4 fold increase in TNF-alpha relative to media baseline. The monomers and dimers were the least stimulatory of the fractions tested, displaying a 42 and 31% increase, respectively, over media control, whereas the trimers, nonamers and decamers showed an intermediate stimulation of this cytokine. In the presence of PHA, the intermediate-sized CFP fractions again were the most active, enhancing TNF-alpha secretion in the range of 48-128% relative to the PHA control. The monomers and dimers were slightly inhibitory (-1.5 and -15%, respectively), while trimers, nonamers and decamers stimulated moderate increases in TNF-alpha levels (13, 19 and 15%, respectively). The above results lend support to the concept that CFP can be immunomodulatory. The stimulation of TNF-alpha secretion may contribute to the putative beneficial effects of dietary flavanoids against microbial infection and tumorigenesis.

Tissue recruitment of dendritic cells (DCs) is essential for antigen presentation. When latex particulates were injected intravenously into rats, DC precursors were recruited to the liver. Propionibacterium acnes also induced the recruitment of definite mouse DC precursors. These DCs initially showed a selective binding to Kupffer cells. In the Kupffer cell-depleted rats, DCs could neither be recruited to the liver nor adhere to sinusoidal walls. Pretreatment with varied monosaccharides in vitro showed that sugar residues consisting of N-acetylgalactosamine were necessary for this binding. Mouse DC precursors had CC-chemokine receptor 1 and 5, while granulama tissues and rat Kupffer cells expressed the corresponding chemokine, macrophage inflammatory protein-lalpha. Recruited DC precursors phagocytosed latex or bacteria and some of them soon translocated to hepatic nodes and induced the immune response there. We conclude that after invasion of pathogens, Kupffer cells not only scavenge them but also recruit DCs/DC precursors via chemokine- and N-acetylgalactosamine-mediated interactions. The accelerated DC traffic and the presence of blood-lymph translocation would induce rapid and efficient immune responses and thus contribute to the local defense to antigens within liver tissues as well as systemic defense to blood-borne antigens.

The reduced quantity and quality of serum immunoglobulins (sIgs) in mutant mice expressing truncated cytoplasmic tails of IgE and IgG1 indicate an active role for the cytoplasmic domains of mIgG1 and mIgE. We used phage display technology to identify candidate proteins able to interact with the cytoplasmic tail of mIgE. Using a murine cDNA B cell library displayed on the surface of phage as prey and the 28 amino acid long cytoplasmic tail of IgE as bait, we isolated phage encoding the murine hematopoietic progenitor kinase 1 (HPK1). Surface plasmon resonance analysis measurements confirmed affinity of HPK1 to the mIgE cytoplasmic tail and revealed association to other immunoglobulin isotypes as well. Immunoprecipitation experiments, using lysates from two B cell lines expressing nitrophenyl (NP) specific mIgE molecules showed co-precipitation of IgE and HPK1. The interaction of HPK1 with the cytoplasmic domains of membrane immunoglobulins indicate an active role of the tails as part of an isotype specific signal transduction, independent from the Igalpha/Igbeta heterodimers, and may represent a missing link to upstream regulatory elements of HPK1 activation.

Allergy and autoimmunity result from dysregulation of the immune system. Until recently, it was generally accepted that the mechanisms that govern these disease processes are quite disparate; however, new discoveries suggest possible common pathogenetic effector pathways. This review illustrates the concomitant presentation of these conditions and the potential relationship or common mechanism in some cases, by looking at the key elements that regulate the immune response in both allergic and autoimmunite conditions: mast cells, antibodies, T cells, cytokines, and genetic determinants. The parallel appearance of allergic and autoimmune conditions in the some patients may reveal that such aberrations of the immune system have a common pathophysiologic mechanism. Mast cells, which play a key role in allergic reactions, and the wealth of inflammatory mediators they express, make it likely that they have profound effects on many autoimmune processes. Activation of protein kinases by inflammatory cytokines and environmental stresses may contribute to both allergic and autoimmune diseases. The presence of autoantibodies in some allergic conditions suggests an autoimmune basis for these conditions. Because of the central role T cells play in immune reactivity, the T-cell receptor (TCR) loci have long been considered important candidates for common disease susceptibility within the immune system such as asthma, atopy, and autoimmunity. Immunomodulation is the key to a successful treatment of allergic and autoimmune conditions.

Adaptive immunity is dependent on proliferation of antigen-driven B cells for clonal expansion in germinal centers (GCs) against T cell-dependent antigens (TD-Ag), accompanied with somatic hypermutation of variable-region gene and class switching of B cell antigen receptors. To study molecular mechanisms for B cell differentiation in GCs, we have identified and studied a 210kDa GANP protein expressed in GC-B cells. GANP has domains for MCM3-binding and RNA-primase activities and is selectively up-regulated in centrocytes surrounded with follicular dendritic cells (FDCs) upon immunization with TD-Ag in vivo and in B cells stimulated with anti-CD40 monoclonal antibody in vitro, which suggested that GANP plays a certain important role in the maturation of immunoglobulin or selection of B cells in GC during the immune response to TD-Ag. Since this up-regulation has not been detected in T cells in GCs and in Concanavalin A-stimulated T cells in vitro, selective function of GANP molecule on B cell proliferation and differentiation might exist.

Although it is well-established that macrophages can occur in distinct activation states, the molecular characteristics of differentially activated macrophages, and particularly those of alternatively activated macrophages (aaMphi), are still poorly unraveled. Recently, we demonstrated that the expression of FIZZ1 and Ym is induced in aaMphi as compared with classically activated macrophages (caMphi), elicited in vitro or developed in vivo during infection with Trypanosoma brucei brucei. In the present study, we analyzed the expression of FIZZ1 and Ym in caMphi and aaMphi elicited during Trypanosoma congolense infection and show that the use of FIZZ1 and Ym for the identification of aaMphi is not limited to T. b. brucei infection and is independent of the organ sources from which macrophages are obtained. We also demonstrate that FIZZ1 can be used to discriminate between different populations of aaMphi. Furthermore, we studied the effects of various stimuli, and combinations thereof, on the expression of FIZZ1 and Ym in macrophages from different mouse strains and demonstrate that regulation of the expression of FIZZ1 and Ym in macrophages is not dependent on the mouse strain. Finally, we show that these genes can be used to monitor the macrophage activation status without the need to obtain pure macrophage populations.

We have identified a novel mAb, SG31, which recognizes the mouse integrin alpha4 subunit. Unlike the epitopes recognized by other anti-alpha4 antibodies, the SG31 epitope is expressed on subpopulations of thymocytes and peripheral T cells. After manganese ion, but not phorbol myristic acetate activation, the epitope is induced and expressed on the majority of peripheral T cells. These data suggest that the SG31 epitope is an activation epitope and that manganese ions activate alpha4 integrins by inducing a conformational change. Comparative flow cytometric analyses showed that the SG31 epitope as well as the epitope detected by other anti-alpha4 antibodies is expressed on all B lineage cells. In the T lineage, expression of the alpha4 integrins is down-regulated during thymocyte development. Although mature thymocytes still express the alpha4 integrins, they lose almost entirely the activation epitope recognized by SG31. In contrast, the most immature thymocytes express high levels of this epitope. In the periphery, SG31 epitope is expressed mostly by activated T cells, in contrast to the overall population of T cells that express the alpha4 integrins at homogenous levels. These results suggest that the activation of the alpha4 integrins is parallel to that of T cells.

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by intrahepatic bile duct destruction and the production of anti-mitochondrial antibodies (AMA). The absence of an animal model has been a striking impedance in defining the molecular basis of disease. Previous work has suggested that SJL/J mice immunize with the pyruvate dehydrogenase complex (PDC-E2), the major mitochondrial autoantigen of PBC, leads to the development of lymphoid cell infiltration in portal tracts and a model system coined autoimmune cholangitis. We hypothesized that this pathology would be augmented if immunization occurred in the presence of IFN-gamma injections. Accordingly, SJL/J mice were immunized with PDC-E2 and, for purpose of control, alpha-casein. Subgroups of mice were also treated with exogenous IFN-gamma. As expected, mice immunized with PDC-E2, with or without IFN-gamma, developed high titer AMAs. In contrast, mice immunized with alpha-casein, develop antinuclear antibodies. More importantly, the livers from mice immunized with PDC-E2 and/or those immunized with alpha-casein all displayed lymphoid cell infiltration to the portal tracts, irrespective of bile duct size. Indeed, there was no significant difference between the experimental and the control groups by histologic analysis. Thus, autoimmune cholangitis in these mice is antigen non-specific.