Immunogenicity of Soluble HL-A Alloantigens

In recent years extensive investigations have been directed toward determining the biologic and chemical profiles of soluble HL-A alloantigens isolated from a variety of tissue sources. During the course of such studies, the in vitro reactivity of these materials was established serologically by their ability to inhibit specifically cytotoxic alloantisera (1). The soluble HL-A antigens have been shown to have further immunologic significance as they can induce specifically blastic transformation of histoincompatible but not of isogeneic leukocytes in vitro (2). Chemical studies thus far suggest that HL-A antigens are essentially protein in nature and apparently consist of single polypeptide chains with a molecular weight of 31,000 (3). The data concerning the immunogenic properties of soluble HL-A alloantigens thus far are scanty and conflicting. Batchelor (4) reported that rabbits immunized with partially purified soluble HL-A substances produced only species-specific lymphocytotoxic antibodies.