A cloned T-cell line from a tolerant mouse represents a novel antigen-specific suppressor cell type

Abstract

Two major alternative models, clonal deletion and suppression, have been proposed as possible explanations for immunological tolerance^1,2. We have now isolated a functional T suppressor (T_s) cell clone to analyse the role of T_s cells in the induction and maintenance of tolerance. This cloned, long-term cultured T_s cell line (HF1) was derived from CBA/J mice (H–2^k) in which low-zone tolerance (LZT)³ had been induced by sub-immunogenic doses of bovine serum albumin (BSA). HF1 cells show BSA-specific suppressor activity in two in vitro suppressor assays. HF1 T_s cells and a factor derived from them suppress imprinted, carrier-specific T helper (T_h) cells in an assay measuring IgG antibody production against fluorescein-conjugated BSA (Flu-BSA). Furthermore, they block DNA synthesis in an antigen-specific in vitro T-cell proliferation assay. Their proliferation in the presence of antigen-presenting cells is antigen specific and shows restriction to the I–A^k region of the major histocompatibility complex (MHC). In addition, HF1 T_s cells have a characteristic cytotoxic activity. The data reported suggest that clonal deletion and suppression models are not necessarily mutually exclusive. Clonal deletion could manifest itself by the action of T_s cells.