An Immunohistochemical Study of Langerhans Cells,T-Cells and the HLA Antigen in Human Cornea

The distribution of Langerhans cells (LC),T-cell subsets andHLA antigen in 12 normal and 7 morbid corneas,including 4 of suppurativecorneal ulcer and 3 of uveogenic endophthalmitis,was investigated withmonoclonal antibodies.The results revealed that a small amount of LC andT-cell subsets were present in the limbal region of normal corneas,whilelarge numbers of LC and OKT_4^+ were observed in the corneas of suppurativeulcer.HLA-A,B,C antigens were expressed on the epithelial cells keratocytes of the normal corneas, while the HLA-DRantigens wereexpressed on the surface of LC at the limbus.

Aetiopathogenesis of autoimmune hepatitis

The histological hallmark of autoimmune hepatitis（AIH） is a dense portal mononuclear cell infiltrate that invades the surrounding parenchyma and comprises T and B lymphocytes,macrophages,and plasma cells.An unknown but powerful stimulus must be promoting the formation of this massive inflammatory cellular reaction that is likely to initiate and perpetuate liver damage.An autoimmune attack can follow different pathways to inflict damage on hepatocytes.Liver damage is likely to be orchestrated by CD4^＋ T lymphocytes recognizing an autoantigenic liver peptide.To trigger an autoimmune response,the peptide must be embraced by an HLA class Ⅱ molecule and presented to naive CD4^＋ T helper（Th0） cells by professional antigen presenting cells,with the co-stimulation of ligand-ligand fostering interaction between the two cells.Th0 cells become activated,differentiate into functional phenotypes according to the cytokines prevailing in the microenvironment and the nature of the antigen,and initiate a cascade of immune reactions determined by the cytokines produced by the activated T cells.Th1 cells,arising in the presence of the macrophage-derived interleukin（IL） -12,secrete mainly IL-2 and interferon-gamma（IFN-γ）,which activate macrophages,enhance expression of HLA classⅠ（increasing liver cell vulnerability to a CD8^＋ T cell cytotoxic attack）,and induce expression of HLA class Ⅱ molecules on hepatocytes.Th2 cells,which differentiate from Th0 if the microenvironment is rich in IL-4,produce mainly IL-4,IL-10,and IL-13 which favour autoantibody production by B lymphocytes.Physiologically,Th1 and Th2 antagonize each other.Th17 cells,a recently described population,arise in the presence of transforming growth factor beta（TGF-β） and IL-6 and appear to have an important effector role in inflammation and autoimmunity.Theprocess of autoantigen recognition is strictly controlled by regulatory mechanisms,such as those exerted by CD4^＋CD25^＋ regulatory T cells,which derive from Th0 in the presence of TGF-β,but in the absence of IL-6.If regulatory mechanisms fail,the autoimmune attack is perpetuated.Over the past three decades different aspects of the above pathogenic scenario have been investigated.In particular,a defect in immunoregulation affecting CD4^＋CD25^＋ regulatory T cells（T-regs） has been demonstrated in AIH,particularly at diagnosis or during relapse.Advances in the study of autoreactive T cells have occurred mostly in AIH type 2,since the knowledge that CYP2D6 is the main autoantigen has enabled the characterization of both CD4 and CD8 T cells targeting this cytochrome.CD4 T cells from patients with type 2 AIH positive for the predisposing HLA allele DRB10701 recognize seven regions of CYP2D6,five of which are also recognized by CD8 T cells.High numbers of IFN-γ producing CD4 T cells and CD8 T cells are associated with biochemical evidence of liver damage,suggesting a combined cellular immune attack.

Anti-human leukocyte antigens and anti-major histocompatibility complex class I-related chain A antibody expression in kidney transplantation during a four-year follow-up

Background Humoral immunity is an important factor for long-term survival of renal allograft. Here we performed a four-year follow-up to explore the clinical significance of monitoring anti-human leukocyte antigens （HLA） and anti-major histocompatibility complex class I-related chain A （MICA） antibody expression after kidney transplantation. Methods We obtained serial serum samples from 84 kidney transplant patients over a four-year period. All patients were followed up at least 6 months after transplantation and had at least two follow-up points. Anti-HLA and anti-MICA antibody titres and serum creatinine （SCr） levels were evaluated at each follow-up. Patients were divided into 4 groups： HLA（＋） MICA（-）, HLA（-）MICA（＋）, HLA（＋）MICA（＋） and HLA（-）MICA（-）. The impact of post-transplant antibody level on kidney allograft function was evaluated. Results Antibodies were detected in 38.1% （32/84） of the renal allograft recipients. HLA, MICA and HLA＋MICA expression was observed in 18.89%, 14.44% and 5.93% of the recipients respectively. The most frequent anti-HLA and anti-MICA specific antibodies identified were All, A24, A29, A32, A33, A80; B7, B13, B37; DR17, DR12, DR18, DR52, DR53, DR1, DR4, DR9, DR51; DQ7, DQ4, DQ8, DQ2, DQ9, DQ5, DQ6 and MICA02, MICA18, MICA19, MICA07, MICA27. As the time after transplantation elapsed, more recipients developed de novo antibody expression. Total 11.91% （10/84） of the recipients had de novo antibody expression during the follow up. The average level of SCr and the percentage of recipients with abnormal allograft function were significantly higher in recipients with anti-HLA and/or anti- MICA antibody expression than those without. The appearance of anti-HLA and anti-MICA antibody expression always preceded the increase in SCr value. Conclusions Anti-HLA and anti-MICA antibody expression has predictive value for early and late allograft dysfunction. The presence of donor specific antibody is detrimental to graft function and graft survival.

Down-regulation of human leukocyte antigens class I on peripheral T lymphocytes and NK cells from subjects in region of high-incidence gastrointestinal tumor

Background Many types of human tumors can suppress the immune system to enhance their survival. Loss or down-regulation of human leukocyte antigens （HLA） class I on tumors is considered to be a major mechanism of tumor immune escape. Our previous studies found that HLA class I on peripheral-blood mononuclear cells was significantly lower in gastric cancer patients. The present study made an analysis of HLA class I expression on peripheral-blood T lymphocytes and NK cells from subjects of Lijiadian village, a village with high-incidence gastrointestinal tumor. Methods A total of 181 villagers from Lijiadian village and 153 normal controls from the Department of Health Examination Center were enrolled in this study. Using a multi-tumor markers detection system, these villagers were divided into two groups： high-risk group （tumor markers positive group） and low-risk group （tumor markers negative group）. The percentage of T lymphocytes and NK cells and levels of HLA class I on their surface were determined in these subjects by flow cytometry. Results Percentages of T lymphocytes and NK cells in peripheral-blood mononuclear cells did not vary with age. The expression level of HLA class I on peripheral T lymphocytes and NK cells was not affected by age or gender, but was significantly down-regulated in Lijiadian villagers （P 〈0.05）, with the low-risk group, there was a significant reduction of cells （P 〈0.05） in the high-risk group. especially on the surface of NK cells （P 〈0.01）. Compared HLA class I on peripheral T lymphocytes （P 〈0.05） and NK Conclusions HLA class I on peripheral T lymphocytes and NK cells may be involved in tumorigenesis and development of gastrointestinal tumor, and understanding their changes in expression may provide new insights into the mechanism of tumor immunity.

The cross-reactivity of I-A^(g7) and I-A^d tetramers

OBJECTIVE: To investigate the cross-reactivity between glutamic acid decarboxylase (GAD)-I-A(g7) and I-A(d) tetramer in diabetes-prone non-obese diabetic (NOD) mice (I-A(g7)) and diabetes-free Balb/c mice (I-A(d)). METHODS: Two GAD peptide I-A(g7) and I-A(d) tetramers were generated and compared for phenotype and function of sorted GAD peptide I-A(g7) and I-A(d) tetramer-positive (tet+) T cells. RESULTS: The cross-reactivity is shown in either tetramer positive percentage or tetramer staining intensity. The NOD and Balb/c derived-tet+ T cells were able to be cross-stained by GAD peptide I-A(g7) and I-A(d) tetramers, and responded to both irradiated NOD and Balb/c splenotyes under stimulation by synthetic and recombinant GAD peptides. CONCLUSION: Although I-A(g7) and I-A(d) are closely related in biochemical and biological aspects, their most notable difference is the presence or absence of a negatively charged residue at position beta57 that links to insulin-dependent diabetes mellitus.