T3⁻ and T3⁺ Cloned Cytotoxic Lymphocytes: Functional and Phenotypic Characteristics

Abstract

Cytotoxic effector cells can be divided into two major groups: 1) Natural Killer (NK) cells, lymphocytes from, e.g., peripheral blood, endowed spontaneous with nonspecific and MHC’ nonrestricted cytolytic activity against NK susceptible target cells such as K562 without deliberate prior antigenic stimulation. Most of these cells also show antibody-dependent cellular cytolysis (ADCC). They generally have the phenotype T3⁻, B73.1⁺, T4⁻, T8^−/+, T11⁺, 0KM1⁺ and the morphological appearance of large granular lymphocytes (LGL). Minor subpopulations with partially different characteristics may also exist; 2) cytotoxic T lymphocytes (CTL) having MHC restricted cytolytic activity after prior antigenic stimulation, e.g., after mixed lymphocyte culture (MLC). Their cytolytic activity is directed against target cells presenting the relevant stimulator antigens. Nonspecific cytolytic activity of MLC responder cells against, e.g., K562 but no ADDC, has been reported earlier (1) and has been defined as activated killer (AK) cell activity. They have the phenotype T3₊, B73.1⁻ and usually T8₊, T11₊, OKM1₋. About 10% of cytolytic T-cell clones are reported to be T3₊, T8⁻, T4⁺ (2).