The Capacity of Class I MHC Molecules To Function as Signal Transduction Elements

Abstract

Class I major histocompatibility complex (MHC) molecules function as restriction elements and recognition structures for antigen-specific cytotoxic T lymphocytes (Berke 1980; Zinkernagel and Doherty 1974, 1979). In addition, class I MHC molecules participate in interactions with CD 8 that facilitate activation of CD 8 positive T cells (Dembic et al. 1987; Geppert and Lipsky 1986; Fleischer et al. 1986). In each case, it is thought that these interactions are principally involved in generating signals in the cell expressing CD 8, the ligand for class I MHC molecules. Little attention has been given to the possibility that these interactions might also deliver signals to the cell expressing the class I MHC molecule. Recent studies, however, have suggested the possibility that class I MHC molecules expressed by T cells may function as signal transducing elements (Geppert et al. 1988, 1989; Gilliland et al. 1989; Mittler et al. 1990; Gur et al. 1990). The signaling capabilities of class I MHC molecules and the possibility that their ligation provides activation signals to T cells are the focus of this review.