SUMMARYCytomegalovirus (CMV) causes severe opportunistic infection in immunocompromised hosts. The importance of conventional ab T cells in protection against CMV infection has been well documented. However, the role of the second T-cell population (which express the cd T-cell receptor) in CMV infection is not known. In the present study, we analysed the function and protective role of cd T cells in a murine cytomegalovirus (MCMV) infection model. After intraperitoneal infection with MCMV, the number of cd T cells increased in the liver and peritoneal cavity from day 3, and reached a peak on day 5. The cd T cells showed an activated T-cell phenotype and predominantly expressed Vc1, which is known to be expressed by heat-shock protein 65 (hsp 65)-speci®c cd T cells. Analysis of cytokine expression demonstrated that the MCMV-induced cd T cells expressed interferon-c (IFN-c) and tumour necrosis factor-a (TNF-a) but not interleukin-4 (IL-4), implying their participation in the cell-mediated immune response against MCMV. Depletion of cd T cells by anti-T-cell receptor (TCR) cd monoclonal antibody (mAb) treatment resulted in signi®cant increase of virus titre and decrease of IFN-c in the liver on day 3 after MCMV infection, which further supports the importance of cd T cells in early protection against infection. Finally, the MCMV-induced cd T cells produced IFN-c in vitro in response to hsp 65. Our results suggest that cd T cells participate in early protection against MCMV infection through recognition of hsp 65 and production of IFN-c.

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Patients with primary biliary cirrhosis (PBC) are usually characterized by the presence of antibody to pyruvate dehydrogenase complex (PDC) in the sera and PDC-specific T cells in the liver. However, most of the patients with PBC do not show peripheral blood T cells response to PDC. In this study, we re-evaluated the peripheral blood T cell responses to PDC in PBC using antigen-presenting dendritic cells (DCs). Twenty-four patients with PBC (AMA-positive: 16; AMA-negative: 8) and 13 normal controls were enrolled in the study. Peripheral blood mononuclear cells (PBMC) and highly enriched populations of T cells were stimulated with either only PDC or DCs plus PDC or PDC-pulsed DC plus PDC. Antibodies to different components of PDC were estimated by an immunoblotting technique. PBMC from only one out of ten AMA-positive PBC patients proliferated when cultured with only PDC. However, peripheral blood T cells from ten out of ten AMA-positive PBC patients and three out of ten AMA-negative PBC patients, but none of the five normal controls showed PDC-specific proliferation when cultured with PDC-pulsed DCs. Two of these three AMA-negative PBC patients, although negative for AMA, were positive for antibodies to other components of PDC. PDC-specific T cells are present in the peripheral blood from most of the patients with PBC. This is the first report on the effectiveness of antigen-pulsed DCs for the elucidation of autoantigen-specific immune response in human autoimmune diseases.