Increased CD45 dimerization in CD45-AP-null cells. CD45 dimerization is increased in the absence of CD45-AP. Thymocytes (A,B) or splenic T cells (C) obtained from wild-type (+) or CD45-AP-null (-) mice were biosynthetically labeled with ³⁵S-labeled amino acids. The cell lysates were treated with or without DSP and immunoprecipitated with anti-CD45 antibody. In panels A and C, the immunoprecipitates were analyzed by nonreducing SDS-PAGE. In panel B, the immunoprecipitate of CD45-AP-null thymocytes was analyzed by 2-dimensional diagonal SDS-PAGE.