HLA-D associated alloantisera react with molecules similar to Ia antigens.

Two human alloantisera specific to bone marrow-derived lymphocytes (B cells) were shown to precipitate polypeptide chains of 29,000 and 34,000 daltons from human lymphoblastoid B cell lines. These molecules are similar to murine Ia antigens and are also precipitated by a rabbit B-cell specific heteroantiserum. Since the alloantisera are thought to recognize determinants coded by HLA-D or closely linked loci, these data support the hypothesis that these B-cell specific alloantigens are the human counterpart of the mouse Ia antigens and may be the products of HLA-D.