Abstract Antibodies against HLA Class II alpha chains were prepared by using as immunogens synthetic peptides selected from the HLA -DQ 1 alpha chains sequence.
Antibodies raised against peptide E2 , a 15-residue fragment of the polymorphic first domain, reacted preferentially with cells with the DQ 1 phenotype; however, despite the low sequence homology of this fragment with corresponding segments in DQw2 and DQw3 alpha chains, a partial crossreactivity with cells not expressing the DQw 1 specificity was detected. Antibodies to peptide H , selected from the monomorphic frame, might be specific for DO alloantigens, and presumably do not react with DR antigens.
The two peptides, in addition, bind anti-Class II antibodies from the serum of a rabbit immunized with human cells, and appear to represent immunogenic linear determinants in the native glycoprotein molecule.