[Primary structure of class II human histocompatibility antigens. 1st communication. Amino acid sequence of the N-terminal 198 residues of the beta chain of a HLA-Dw2,2;DR2,2-alloantigen (author's transl)].

The beta-chains of HLA-D/DR antigens from a lymphoblastoid homozygous cell line (HLA-A3,3;B7,7;-Dw2,2;DR2,2) were purified by an exclusively chemical three step procedure: 1) Nonidet P-40/CM-cellulose ion-exchange-, 2) Na-dodecyl sulfate/sephacryl S-300- and 3) Na-dodecyl sulfate/hydroxylapatite chromatography. The amino acid sequence of the beta chain was established up to position 198. These residues comprise the extra-cellular part of the molecule which consists of two domains each probably containing a disulfide bridge, like immunoglobulin L chains. Within the first domain the carbohydrate moiety is attached to asparagine in position 19. Sequence work was hampered by the fact that the beta chain preparation of the HLA-Dw2,2;DR2,2 antigen actually consists of a pool of beta chains. The beta chain, the sequence of which has now been established, represents about 70% of the beta chain pool. The remaining 30% consist of at least 6 more chains which are homologous among one another as well as to the described beta chain. Since the antigens were gained from a homozygous lymphoblastoid cell-line our results indicate that the HLA-D region codes for at least 7 beta-chains and must therefore consist of a cluster of beta chain genes.