The molecular specificities of DS-specific reagents: an MB3-like monoclonal antibody isolates two DS molecules.

HLA-DS molecules are the human homologues of murine I-A molecules. The molecular specificities of four anti-DS reagents were examined by two-dimensional gel electrophoresis in light of the recent evidence that HLA-DR homozygous cell lines express at least two DS molecules. Each of the DS-specific reagents, including the IVD12 monoclonal antibody which defines an MB3-like determinant, isolated at least two DS molecules from a DR5 homozygous cell line. Because previous studies of this cell line documented that anti-MB3 allosera isolated only one DS molecule, these data indicate that there is heterogeneity of the molecular specificities of anti-Ia reagents that are specific for the MB3 allodeterminant or the MB3-like determinant in population studies.