Separation of helper T cells from suppressor T cells expressing different Ly components. II. Activation by antigen: after immunization, antigen-specific suppressor and helper activities are mediated by distinct T-cell subclasses.

Abstract

Cells of the Lyl subclass generate helper activity in both primary and secondary responses to sheep erythrocytes (SRBC). In contrast, after priming with SRBC, cells of the Ly-2+ subclasses, in particular Ly23 cells, have suppressive activity. The degree of Ly23-mediated suppression is directly proportional to the amount of antigen (SRBC) used for priming. Suppression by Ly23 cells is specific, because Ly23 cells from SRBC-primed animals do not suppress the response to horse erythrocytes, and vice versa. Thus, both cytotoxic and specific suppressor functions are mediated by T cells of a subclass, provisionally designated TCS, which can be distinguished from helper T cells (TH), by their Ly phenotypes. It remains to be determined whether killing and suppression are functionally interrelated properties of a single Ly23 subclass, or whether the Ly23 population comprises two subclasses whose surface phenotypes are not yet distinguishable by immunogenetic criteria.