Immunity protects animals from infectious diseases. Certain T lymphocytes regulate immunity in a highly-selective manner. These cells distinguish self tissue from foreign antigen. Membrane glycoproteins encoded by a gene cluster termed H-2 in the mouse occur on accessory cells and B lymphocytes with which regulatory T cells interact. These glycoproteins are involved in the process by which foreign antigen is rendered immunogenic, and thereby influence regulatory T cell induction. The molecular basis for immune regulation is not completely understood. Isolating and characterizing important immunoregulatory molecules has proven difficult. An alternative approach is to isolate the genes involved in regulating immunity by gene cloning. Proteins encoded by these genes can then be obtained in sufficient quantity to permit biochemical characterization and biological investigation. The specific aim of this proposal is to clone the genes encoding two important T lymphocyte membrane glycoproteins. Neither glycoprotein has been isolated from T cells and characterized biochemically. One, the I-J glycoprotein, demarcates a suppressive class of T lymphocytes responsible for impeding immunity. The other, I-At glycoprotein, characterizes and augmenting class of T lymphocytes responsible for enhancing immunity. The regulating activities of augmenting and suppressive T lymphocytes are antagonistic. Our preliminary results suggest that both glycoproteins participate in the process by which T cells distinguish foreign antigen; they may form part of a T cell receptor structure that binds antigen. We plan to achieve our goal by producing cell lines that biosynthesize significant quantities of the I-J and I-At glycoproteins. Messenger RNA derived from the cell lines will serve as a template for cDNA synthesis; cDNA will be cloned using an innovative scheme designed to facilitate eukaryotic gene expression in bacteria. Translated proteins will be detected immunochemically. Should this scheme prove unsuitable, alternative strategies are proposed.