A lectin-binding soluble factor released by CD8+CD57+ lymphocytes from AIDS patients inhibits T cell cytotoxicity.

CD8+CD57+ T cells, expanded in peripheral blood lymphocytes of AIDS patients, inhibit the effector phase of HLA-specific cytotoxic T lymphocytes, natural killer and lymphocyte-activated killer cells in a 4-h chromium-release assay. This inhibitory activity present in supernatants of purified sorted CD8+CD57+ cells is mediated by a non-antigen-specific inhibitory factor which is distinct from prostaglandin E2, T cell growth factor (TGF)-beta, latent-TGF-beta, tumor necrosis factor (TNF)-alpha and TNF-beta. Partial biochemical characterization demonstrates that the CD8+CD57+ inhibitory activity (a) is heat, trypsin and acid resistant, (b) binds to concanavalin A columns, indicating its glycosylation state and (c) is mediated by a 20-30-kDa soluble molecule.