Association of Ly phenotypes, T cell function and MHC recognition.

Lyt molecules has been exceptionally useful in defining district subpopulations of T lymphocytes. In this paper the significance of the association of Lyt phenotypes of T cells with their specialized functions and with their recognition of different major histocompatibility complex (MHC) subregions is examined. The published data, which indicates that helper activity stimulated by allogeneic Class I (K/D) antigens is dependent on a mature Ly123 cell that does not interact with an Ly1 cell (conventional helper), is reviewed. Recent studies, which show that a long-term allospecific cell line with killer activity directed against an Ia antigen is an Ly1 cell with expression of Lyt2, are presented. It is concluded that Lyt2 molecules are not themselves required for the induction or delivery of killing. It is suggested that Lyt molecules may not be reliable markers of the functional commitment of T cells and that Lyt phenotypes may be better correlated with the subregion of the MHC that such T cells recognize.