乙型肝炎病毒感染对机体免疫功能影响的研究进展

机体免疫功能的紊乱是乙型肝炎发病的重要因素.HBV感染可以引起多种免疫细胞(如DC、淋巴细胞、NK/NKT细胞)的功能障碍,包括表面分子表达的异常,分泌细胞因子的异常和亚型比例失调等.凋亡也是肝组织损伤和淋巴细胞功能障碍的原因之一.     

Presentation of alpha-galactosylceramide by murine CD1d to natural killer T cells is facilitated by plasma membrane glycolipid rafts

CD1 molecules are non-polymorphic major histocompatibility complex class I-related proteins that bind and present glycolipid antigens to T-cell antigen receptors (TCR) expressed by alphabeta T cells or natural killer-like T cells (NKT). Anti-metastatic properties of NKT cells reactive to the CD1d-binding antigen alpha-galactosylceramide (alpha-GalCer) are now being explored as a contributor to tumour cell killing. In this study, we tested the hypothesis that presentation of alpha-GalCer by murine CD1d (mCD1d) to mCD1d-restricted NKT cells was facilitated by plasma membrane glycolipid rafts. Confocal microscopy of mCD1d-transfected A20 B cells (A20mCD1d) demonstrated that mCD1d was raft-localized. This observation was confirmed by immunoblotting of raft fractions isolated on sucrose density gradients. Raft disruption by the cholesterol-binding agent nystatin, or short-chain ceramides, inhibited presentation of low concentrations of alpha-GalCer to NKT cells. Inhibition of antigen presentation was reversed by treatment of A20mCD1d cells with higher alpha-GalCer concentrations, or removal of raft-disrupting agents. These data indicate that partitioning of mCD1d into membrane rafts increases the capacity of antigen-presenting cells to present limiting quantities of glycolipid antigens, perhaps by stabilizing mCD1d/antigen structures on the plasma membrane and optimizing TCR engagement on NKT cells.     

Oligomeric MHC molecules and their homologues: state of the art

This special issue of the Journal of Immunological Methods brings together articles from some of the leaders in labelling antigen-specific T and NKT cells, describing recent technical advances and their impact on the study of immunology. Although tetramers, or tetrameric MHC class I/peptide complexes, are the best known reagents in the field, various forms of oligomeric complexes are now being successfully used to detect antigen-specific T cells, including cytotoxic T lymphocytes, MHC class II-restricted CD4+ T cells, and glycolipid-specific T cells restricted by CD1 isoforms. The articles presented here detail the breadth of the oligomeric structures being used to probe T, NK and NKT cell function, and cover both the technical and practical aspects of their use, as well as the new biology revealed. In addition to providing a summary of the current state of the art, these contributions also provide clear pointers to strategies likely to succeed in the future. In this introductory chapter, we summarise the work presented in the other articles of this issue, and provide an overarching view of this rapidly evolving field. We also provide a summary of the MHC class I molecules successfully refolded to date, and provide references to other relevant sources of technical information.     

CD1d deficiency exacerbates inflammatory dermatitis in MRL-lpr/lpr mice

Mechanisms responsible for the development of autoimmune skin disease in humans and animal models with lupus remain poorly understood. In this study, we have investigated the role of CD1d, an antigen-presenting molecule known to activate natural killer T cells, in the development of inflammatory dermatitis in lupus-susceptible MRL-lpr/lpr mice. In particular, we have established MRL-lpr/lpr mice carrying a germ-line deletion of the CD1d genes. We demonstrate that CD1d-deficient MRL-lpr/lpr mice, as compared with wild-type littermates, have more frequent and more severe skin disease, with increased local infiltration with mast cells, lymphocytes and dendritic cells, including Langerhans cells. CD1d-deficient MRL-lpr/lpr mice had increased prevalence of CD4(+) T cells in the spleen and liver and of TCR alpha beta (+)B220(+) cells in lymph nodes. Furthermore, CD1d deficiency was associated with decreased T cell production of type 2 cytokines and increased or unchanged type 1 cytokines. These findings indicate a regulatory role of CD1d in inflammatory dermatitis. Understanding the mechanisms by which CD1d deficiency results in splenic T cell expansion and cytokine alterations, with increased dermal infiltration of dendritic cells and lymphocytes in MRL-lpr/lpr mice, will have implications for the pathogenesis of inflammatory skin diseases.     

Immunoregulatory defects of V alpha 24V+ beta 11+ NKT cells in development of Wegener's granulomatosis and relapsing polychondritis

The frequency of either CD4(-)8(-) (double negative; DN) or CD4(+) V alpha 24(+)V beta 11(+) NKT cells, the expression of CD1d and the binding of CD1d-tetramer loaded with alpha-galactosylceramide (alpha-GalCer) to NKT cells were analysed in peripheral blood mononuclear cells (PBMCs) of patients with Wegener's granulomatosis (WG), relapsing polychondritis (RP) and healthy subjects (HS). DN and CD4(+) V alpha 24(+)V beta 11(+) NKT cells as well as CD1d-alpha-GalCer tetramer-positive NKT cells, were significantly decreased in number in both WG and RP patients compared to those from HS. When cytokine profiles were analysed in these PBMCs upon stimulation with phorbol ester and calcium ionophore, CD4(+) T cells from patients with WG and RP exhibited a Th1 bias, whereas CD4(+) NKT cells from WG patients in remission showed a Th2 bias. These findings suggest that NKT cells (especially CD4(+) NKT cells) play a regulatory role in Th1 autoimmunity in patients with WG and RP. The reduction in NKT cell counts appears to be associated with the low responsiveness to alpha-GalCer. The dysfunction of NKT cells to recognize ligands such as alpha-GalCer may also contribute to the defects observed in NKT cells from WG and RP patients.     

Analysis of evolutionary conservation in CD1d molecules among primates

The hereditary conservation in the genetically encoded CD1D sequences of various primates was analyzed. Genomic CD1D sequences of 17 rhesus macaques with distinct origins, eight Indian and nine Chinese, were examined and differences of only one or two nucleotides were detected and the consensus sequence of rhesus CD1D was determined. CD1D consensus sequences of three African green monkeys (AGMs) and the rhesus monkeys were then compared to study the evolutionary differences among interspecies. The CD1D consensus sequence determined from AGMs apparently differed by seven nucleotides from the rhesus consensus sequence, and nucleotide difference induced only three amino acid changes within Exon3, corresponding to the alpha2 domain of CD1d having a hydrophobic ligand-binding pocket. Such changes in the alpha2 domain may alter the characteristics of the SIV-derived glycolipid/lipid antigens presented by each CD1d molecule to innate natural killer T cells. In addition, the CD1D genomic sequences of three chimpanzees (chimps) were determined. To our surprise, although Exon2 and Exon3 reflecting antigen-binding alpha1 and alpha2 domains in chimps' CD1D were identical to that in humans except one amino acid, three amino acids within Exon4, reflecting alpha3 domain, were distinct from humans, and one of them was identical to those in rhesus and AGM CD1D. On the basis of the findings, the evolutionary relationship of the CD1d molecules among the various primates and their HIV-1/SIV susceptibility will be discussed.     

免疫应答类型的重新分类

过渡性免疫应答由原属固有免疫应答的原始B1细胞、γδT细胞和NKT细胞所组成.其中原始B1细胞承担过渡性免疫应答的体液免疫,γδT细胞和NKT细胞承担过渡性免疫应答的细胞免疫,主要识别和排除TI抗原.固有免疫应答的细胞包括吞噬细胞、树突状细胞、NK细胞等,体液免疫组包括补体、急性期蛋白、溶菌酶等,其主要作用是非特异性地清除或递呈抗原.适应性免疫应答的细胞由B2细胞和αβT细胞组成,B2细胞承担适应性体液免疫应答,αβT细胞承担适应性细胞免疫应答,主要识别和排除胸腺依赖性抗原(TD).免疫应答分为3种类型是对免疫系统进化的客观阐述,符合物种进化的基本规律,准确反映了免疫功能的发生和发展,对完善免疫学基础理论以及指导临床免疫学研究具有重要的意义.     

Suppression of eosinophilic airway inflammation by treatment with alpha-galactosylceramide

To clarify the essential role of NKT cells in allergy, we investigated the contribution of NKT cells to the pathogenesis of eosinophilic airway inflammation using alpha-galactosylceramide (alpha-GalCer), a selective ligand for NKT cells. Although continuous administration of alpha-GalCer during ovalbumin (OVA) sensitization increased OVA-specific IgE levels and worsened eosinophil inflammation, a single administration of alpha-GalCer at the time of OVA challenge completely prevented eosinophilic infiltration in wild-type mice. This inhibitory effect of alpha-GalCer was associated with a decrease in airway hyperresponsiveness, an increase in IFN-gamma, and decreases in IL-4, IL-5 and IL-13 levels in the bronchoalveolar lavage fluids. Analysis of lung lymphocytes revealed that production of IFN-gamma increased in NK cells, but not in T or NKT cells, following alpha-GalCer administration. Induction of vascular cell adhesion molecule-1 in the lungs of wild-type mice was also significantly attenuated by treatment with alpha-GalCer. These effects of alpha-GalCer were abrogated in J alpha281-/- mice, which lack NKT cells, and in wild-type mice treated with anti-IFN-gamma Ab. Hence, our data indicate that alpha-GalCer suppresses allergen-induced eosinophilic airway inflammation, possibly by inducing a Th1 bias that results in inhibition of eosinophil adhesion to the lung vessels.     

Requirement for IFN-gamma in IL-12 production induced by collaboration between v(alpha)14(+) NKT cells and antigen-presenting cells

Two cytokines IL-4 and IL-12 are known to determine the balance between T(h)1 and T(h)2 development. In addition to IL-4 production of V(alpha)14(+) NKT cells, they have recently been demonstrated to have the capacity to stimulate IL-12 production by antigen-presenting cells (APC). This study demonstrates that IFN-gamma is absolutely required for the NKT cell-stimulated IL-12 production. Culture of B cell-depleted spleen cells from C57BL/6 mice with alpha-galactosylceramide (alpha-GalCer) capable of selectively stimulating V(alpha)14/J(alpha)281(+) NKT cells resulted in the production of IL-12 together with IL-4. Whereas IL-4 production occurred in culture of IFN-gamma(-/-) C57BL/6 splenocytes, the same culture failed to generate IL-12 production. While IL-12 production induced during culture of V(alpha)14(+) NKT cells and APC depended on the interaction between CD40 ligand on NKT cells and CD40 on APC, the expression levels of these key molecules were comparable in cells from wild-type and IFN-gamma(-/-) mice. Addition of rIFN-gamma to alpha-GalCer stimulated IFN-gamma(-/-) splenocyte culture, and administration of rIFN-gamma to alpha-GalCer-injected IFN-gamma(-/-) mice resulted in the restoration of IL-12 production in vitro and in vivo. These results illustrate a mandatory role for IFN-gamma in V(alpha)14(+) NKT cell-stimulated IL-12 production by APC.     

CD1d-restricted NKT cells contribute to malarial splenomegaly and enhance parasite-specific antibody responses

CD1d-restricted NKT cells are a novel T cell lineage with unusual features. They co-express some NK cell receptors and recognize glycolipid antigens through an invariant T cell receptor (TCR) in the context of CD1d molecules. Upon activation through the TCR, NKT cells produce large amounts of IFN-gamma and IL-4. It has been proposed that rapid cytokine output by activated NKT cells may induce bystander activation of other lymphoid lineages. The impact of CD1d-restricted NKT cell activation in the induction of B cell-mediated immune responses to infection is still unclear. We show here that CD1-restricted NKT cells contribute to malarial splenomegaly associated with expansion of the splenic B cell pool and enhance parasite-specific antibody formation in response to Plasmodium berghei infection. The increased B cell-mediated response correlates with the ability of NKT cells to promote Th2 immune responses. Additionally, antibody responses against the glycosylphosphatidylinositol (GPI)-anchored protein merozoite surface protein 1 (MSP-1) were found to be significantly lower in CD1(-/-) mice compared to wild-type animals. P. berghei-infected MHC class II (MHCII)(-/-) mice also generated antibodies against MSP-1, suggesting that antibody production against GPI-anchored antigens in response to malaria infection can arise from both MHCII-dependent and independent pathways.