A new allodeterminant on HLA-DQ molecules carrying the DQw3 specificity.

The la subset that reacts with alloantiserum HON known to possess a strong anti-DRw53 activity was isolated from a 125I-labeled Ia preparation obtained from cells of RPMI 8057 cell line (DR1,4) and was found on peptide mapping to be lacking in the pattern characteristic of DR-like molecules carrying the DRw53 specificity and to display the structural features of DQ molecules, particularly those carrying the DQw3 specificity. Distribution analysis on a panel of selected la-positive cell lines indicated that the specificity involved is associated only with DR4 and DRw9, differing from the known DRw53 pattern (DR4, 7, and w9) and also from the known DQw3 pattern (DR4 and 5). Reciprocal sequential binding experiments demonstrated that the HON-defined specificity resides along with DQw3 specificity on the same molecules. Thus, HON alloantiserum possesses two different antibody activities; one directed to DRw53 specificity and another directed to a new DR4- and w9-associated DQ specificity.