Multiple Histocompatibility Complex Class Research Articles

Infection of mouse bone marrow-derived dendritic cells with recombinant adenovirus vectors leads to presentation of encoded antigen by both MHC class I and class II molecules—potential benefits in vaccine design

Dendritic cells (DCs) are highly specialised antigen-presenting cells (APCs) that are essential for the initiation and modulation of T cell-mediated immune responses. In order to induce effective CTL responses against most infections and tumours, DCs must prime both CD4 + and CD8 + antigen-specific T cells. It is, therefore, important in vaccine design to produce antigen-delivery systems that lead to the simultaneous presentation of multiple histocompatibility complex (MHC) class I- and class II-restricted antigenic peptides by DCs. In this study, the infection of immature mouse bone marrow-derived DCs (BMDCs) with recombinant adenovirus (rAd) vectors led to a marked upregulation of surface costimulatory molecules, IL-12 p40 production and capacity to stimulate both allogeneic and antigen-specific T cells. Furthermore, infection of immature and mature BMDCs with a rAd encoding chicken ovalbumin (OVA) led to presentation of the antigen to TCR-transgenic OVA-specific CD4 + and CD8 + T cells. In addition, the activation state of responding CD8 + T cells was further amplified if they recognised antigen on rAd-transduced BMDCs in the presence of antigen-specific CD4 + T cells. The results suggest that rAd-encoded OVA protein is secreted by BMDCs, taken up by endocytosis and presented in association with MHC class II molecules for activation of OVA-specific CD4 + T cells. Consequently, rAd-transduced immature BMDCs become better stimulators of antigen-specific CD4 + T cells than rAd-infected mature BMDCs. Taken together, these data have important implications for vaccine design, and suggest that infection of immature DCs with rAd encoding MHC class I and class II-restricted T cell epitopes could be an efficient means of inducing effective immune responses.

Down-regulation of interferon-γ signaling by gene transfer of Stat1 mutant in mesangial cells

Interferon-gamma (IFN-gamma) is secreted by T lymphocytes and natural killer (NK) cells in the cellular immunity-mediated inflammatory lesion, including endocapillary or extracapillary proliferative glomerulonephritis. It induces and/or enhances multiple histocompatibility complex (MHC) class I and II, intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS), and Fc receptor expression in renal resident cells, resulting in the initiation and promotion of inflammation. Recently, the signaling mechanism of IFN-gamma has been investigated, and it appears that Stat1alpha is essential for signaling. We investigated Stat1alpha activation by IFN-gamma in mesangial cells and attempted to regulate the signal transduction by gene transfer. Western blot with anti-Stat1 and antiphosphotyrosine after immunoprecipitation of Stat1 and Northern blot for detection of Stat1 mRNA were performed. The dominant negative form of Flag-tagged Stat1 was expressed in cultured rat mesangial cells. Flag was immunostained in transfectants, and luciferase reporter assay was carried out to measure the transcriptional activity of Stat1alpha. The expression of IFN-gamma-inducible genes such as MHC class II (Ia-Aalpha) and MHC class II transactivator (CIITA) was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Stat1alpha was tyrosine phosphorylated and activated by IFN-gamma in mesangial cells, and the mRNA and protein level of Stat1alpha increased upon stimulation by IFN-gamma. Overexpression of Stat1-mutant lacking 35 C-terminal amino acids strongly suppressed the IFN-gamma-induced signal transduction and inhibited the expression of MHC class II and CIITA genes in mesangial cells. Stat1alpha is a critical molecule in the signal transduction of IFN-gamma in mesangial cells. The inhibition of an endogenous function of Stat1alpha by gene transfer of the Stat1 mutant may be a new method to reduce the inflammatory effects of IFN-gamma in localized inflammation of the kidney.

Sharing cross-reactive groups of MHC class I improves long-term graft survival

Renal transplant loss from chronic rejection remains substantial. To increase our understanding of this syndrome, we identified risk factors predicting late graft loss, with a special emphasis on the impact of human lymphocyte antigen (HLA) matching. We studied all 654 cadaveric kidney transplants performed in our center between 1983 and 1996 that had survived for more than six months. Eighty-two transplants, lost because of chronic rejection, were used as the outcome variable. The influence of HLA mismatches and shares on long-term graft survival was evaluated at the level of private antigens and cross-reactive groups (CREG) of multiple histocompatibility complex (MHC) class I. HLA and other recipient, donors and transplant parameters were studied using univariate and multivariate Cox regression analysis. The cohort had a mean number of 1.9 HLA mismatches. Because of the homozygosity of HLA antigens, HLA mismatches were not reciprocal to shares. CREG and HLA-A-B mismatches had a relative risk for graft loss of 1.19 (95% CI, 0.97 to 1.45) and 1.05 (0.84 to 1.32) per mismatch. In contrast, the relative risk per shared CREG and broad HLA-A-B antigen was 0.76 (0.63 to 0.92) and 0.79 (0.61 to 1.03). Multivariate analysis revealed that individuals sharing less than four CREGs had a relative risk of 2.13 (1.29 to 3.75) for late graft loss. Other independent predictors were a recipient age of less than 50 years, relative risk 1.95 (1.02 to 3.71); a donor age of more than 50 years, relative risk 1.68 (1.01 to 2.80); acute rejection (vascular vs. no rejection), relative risk 3.52 (1.72 to 7.18); proteinuria (dipstick > 1+ vs. negative), relative risk 2.86 (1.29 to 6.35); and a serum creatinine concentration of more than 150 micromol/liter at six months, relative risk 3.41 (1.96 to 5.94). We identified several coexisting recipient-, donor-, and transplant-related risk factors for graft loss from chronic rejection. In this well-matched group of renal transplants, HLA mismatches and shares had a nonreciprocal relationship. Sharing of HLA antigens, especially CREG of MHC class I, was associated with improved long-term survival.