51] Purification and molecular cloning of Rat Ia antigens

Abstract

This chapter describes the purification of Ia glycoproteins from detergent solubilized rat spleen membranes using monoclonal antibody affinity chromatography and the characterization of the purified Ia molecules. Methods are also described for the purification of mRNA from rat spleen and the molecular cloning of cDNA coding for rat Ia-A antigens. The chapter reviews that the Ia antigens are a set of highly polymorphic cell surface molecules involved in many cell-cell interactions and coded for by the major histocompatibility complex (MHC). The polymorphism of the Ia antigens is directly related to their function, as these molecules are thought to be the products of the immune response genes which genetically determine the outcome of many types of immune responses. These have been identified in several different mammalian species and are composed of two noncovalently bonded glycosylated polypeptides referred to as the α and β chains. The chapter also discusses that the Ia glycoproteins show a restricted tissue distribution being present on B lymphocytes, dendritic cells, some macrophages and thymocytes, and on epithelial and reticular cells of thymus and spleen. These molecules are not generally found on the majority of T lymphocytes or other cells. The rat MHC, called the RT1 complex, codes for two sets of Ia antigens referred to as Ia-A and Ia-E which correlate to the mouse H-2 I-A and I-E Ia antigens.