1086 Mechanisms of Regulation of Cell - Mediated

The existence of regulatory molecules derived from T cells, which play an important role in the control of immune reactions, has been documented in a number of experimental systems (1-4). Such T-cell-derived regulatory molecules appear to share many biochemical properties which would argue for their structural and functional similarity (3, 4). These common properties support the notion that similar gene families may be responsible for encoding the structural components of such regulatory factors. In addition to antigenic specificity, many suppressor factors contain determinants which are controlled by the major histocompatibility complex. These H-2-region determinants are usually, (3-5) but not always (6), encoded by genes which map at the I-J subregion. In the companion paper (7) it has been established that p-azobenzenearsonate (ABA) Ispecific suppressor T cells elaborate a product which shares many of the known structural features of specific suppressor factors (3-6). ABA-specific suppressor factor(s) are proteins, with a molecular weight between 33 and 68,000 daltons, which do not bear antigenic determinants of the constant regions of conventional immunoglobulin (7) but contain antigenic determinants coded for by the K end of the H-2 major histocompatibility complex (MHC) (7). The presence of both antigen-binding specificity and major histocompatibility complex gene products in soluble T-cell-derived antigen-specific suppressor material permits analysis of gene products concerned with the structure of antigen-specific molecules derived from T cells. The ABA specificity was chosen because of the extensive data available relating to the nature of the cross-reactive idiotype (CRI) evoked in A/J mice immunized with ABA-keyhole limpet hemocyanin (KLH) (8).