Immune response region‐associated antigens of the mouse. Biochemical properties of detergent and papain solubilized molecules

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Abstract
Immune response region‐associated (Ia) antigens and classical H‐2 antigens are glycoproteins which differ in their molecular weight and tissue distribution. Ia and H‐2 molecules also show differences in overall charge, apparent isoelectric point and susceptibility to proteolytic degradation, acid treatment and exposure to 56°C. In the present paper, Ia.11d antigens were shown to have a molecular weight of about 35 000 after solubilization with non‐ ionic detergents. Purified Iad antigens, solubilized by controlled papain digestion, display a molecular weight of about 26 000 after final purification by indirect immune coprecipitation. This figure corresponds to the molecular weight of a highly purified H‐2 polypeptide fragment obtained after papain solubilization. The remarkable size similarity of proteolytic fragments from Ia and H‐2 antigens could suggest that these genetically and functionally related molecules possess some structural features in common.