Analysis of Human Class II Antigen a Chain Genes: A Summary Charles Auffray, Alan J. Korman, Magali Roux-Dosseto, Anton Schamboeck, and Jack L. Strominger ABSTRACT: A cDNA clone corresponding to the HLA-DRa chain has been isolated following im- munoprecipitation of polysomes with a monoclonal antibody against the denatured DR~ chain. This cDNA clone has been used to isolate and solve the complete structure of the DRct chain gene and a cDNA clone corresponding to the DCce chain. The DRc~ and the DCc~ chains bear remarkable homology to each other and have one domain (02) which is a member of the immu- noglobulin superfamily. The DCce chain gene has been demonstrated to be the homologue of the murine I-Ac~ chain gene, and it has been localized on chromosome 6 using deletion mutants. A restriction enzyme polymorphism of the DC~ chain gene has been detected in HLA-DR homozygous typing cells. This report is a summary of a presentation made at the HLA-DR meeting held in Marseille. France. ISOLATION OF cDNA CLONES CORRESPONDING TO THE DR a CHAIN mRNA A murine monoclonal antibody has been produced after immunization with the denatured DR~ chain. This antibody has been used to characterize the cell-free translation products of the DRc~ chain mRNA. It was subsequently used to immunopurify polysomes on which the nascent DR~ chain is synthesized in B lymphocytes [1]. This resulted in a 3000-fold purification of the DR~ chain mRNA which represents only 0.02% of the total poly(A) mRNA. The immu- nopurified mRNA was used to obtain cDNA clones either directly or by screening a cDNA library, cDNA clones obtained by both methods were shown to cor- respond to a copy of the DR~ chain mRNA by their ability to select this mRNA specifically. DNA sequencing experiments further demonstrated that one clone, pDRH2, contains the sequence coding for the carboxyterminal part of the DRa chain, a result which was confirmed by carboxypeptidase digestion of the DRc~ chain. From the Department of Biochemistr 3, and Molecular Biology. Harvard University, Cambridge, MA 02138. Address requests for reprints to Dr. Charles Auffray, Department of Biochemistry and Molecular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138. Received April 26, 1983," accepted April 27. 1983. Human Immunology 8, 89-93 (1983) © Elsevier Science Publishing Co., Inc., 1983 52 Vanderbilt Ave., New York, NY 10017 89 0198-8859/83/$3.0(}