Anti-Fas antibodies induce cytolysis and apoptosis in cultured human mesangial cells

Death of renal cells often occurs during the acute and resolution phases of some forms of glomerulonephritis. The apoptotic Fas protein belongs to a recently described family of cytokine receptors with similarities to tumor necrosis factor (TNF) receptors, and may contribute to the necrobiology of renal cells. Fas transduces a signal for apoptosis in sensitive cells after binding by specific antibodies or following contact with natural Fas ligand. We have studied Fas in cultured human mesangial cells. Cytoflurography demonstrated Fas expression on the surface of human mesangial cells that was increased by stimulation with interferon gamma (IFN gamma). Agonistic anti-human Fas antibodies were cytotoxic to these cells. Cytotoxicity was time- and dose-dependent, and was modulated by pre-stimulation of the mesangial cells with IFN gamma and/or by co-treatment with actinomycin-D. Mesangial cell death following exposure to anti-Fas antibodies has features consistent with apoptosis, such as internucleosomal DNA fragmentation, nuclear shrinkage and condensation, and decreased DNA content. These data suggest that Fas and its ligand could play a mechanistic role in human glomerular cell injury.

HLA-target antigens and T-cell receptor diversity of activated T cells invading the skin during acute graft-versus-host disease

To study the repertoire and specificity of T lymphocytes infiltrating skin lesions during graft-versus-host disease (GVHD), we performed an exhaustive molecular and functional analysis of 146 T-cell clones derived from the skin of three patients undergoing an acute GVHD after allogeneic bone marrow transplantation (BMT) from HLA-mismatched related donors. Analysis of T-cell receptor (TCR) rearrangement and TCR chain junctional sequences demonstrated the presence of 11 distinct clones among the 64 derived from patient UPN1, six among the 58 derived from patient UPN2, and seven among the 24 derived from patient UPN3. Three of the 11 T-cell clones from patient UPN1, and all clones from patients UPN2 and UPN3 reacted with mismatched HLA alleles between the bone-marrow donor and recipient. Moreover, both HLA class I (HLA-A2 and -B27) and class II (HLA DP101, DP401, DP1301, DQ8, and DR402) molecules were recognized during this early antihost response. Finally, both TCR alpha and beta chains turned out to be extremely diverse, even within populations of clones derived from the same patient and directed against the same HLA allele. Taken together, these results indicate that any HLA mismatch is potentially targeted during early GVHD, and that the T-cell response at the onset of GVHD is both oligoclonal and highly diversified.