Further Biochemical Studies of the Human B-Cell Differentiation Antigens B1 and B2

Two human B lymphocyte-associated antigens, B1 and B2, were studied by immunoprecipitation using monoclonal antibodies. B1 was found to be a nonglycosylated protein of MW 35 kD, phosphorylated at serine and threonine. B2, a 140 kD MW antigen, was characterized as a glycoprotein without phosphorylated sites. Both proteins were found to contain portions which could be labeled with ¹²⁵I-iodonaphthylazide. The B1 protein displayed hydrophobic properties whereas B2 had a more amphiphilic character.