Immunological and chemical purity of papain-solubilized HL-A antigens

Three preparations of purified papain-solublized HL-A antigens have been radiolabeled by reductive methylation using formaldehyde and potassium boro[3H]hydride, and their reaction with specific HL-A antisera has been investigated. Greater than 99 percent of the radioactivity in the [3H]HL-A2 preparation could be complexed with several HL-A2 antisera, but not with specificity controls. The other two preparations, which contained mixtures of HL-A antigenic specificities (HL-A7,12 an HL-A3,W25;12,27), showed 63 per cent and 70 per cent complex formation with mixtures of the appropriate HL-A antisera. The N-terminal amino acid of both subunits has been determined for the three HL-A antigen preparations. In all cases the only detectable N-terminal amino acids were isoleucine for the small subunits, beta-2-microblogulin, and glycine for the larger subunit.