Biochemical studies of Xenopus laevis lymphocytes surface immunoglobulins.

Cell surface immunoglobulins of adult Xenopus laevis splenic small lymphocytes were analysed utilizing direct immunofluorescent staining and lactoperoxidase-catalysed radioiodination followed by immunoprecipitation of Ig molecules and characterization on SDS-PAGE. Nearly 30% of splenic lymphocytes are surface Ig positive. The HMW and LMW Ig classes are present on the surface of 23% and less than 5% of the cells, respectively. The mu chains of membrane HMW Ig have an apparent m.w. of 84,000 versus 73,000 for the mu chains of serum HMW Ig. Using immunofluorescent technique, we previously reported the absence of Ig molecules on the surface of larval Xenopus thymocytes. When the lactoperoxidase radioiodination technique was used, no cell surface Ig molecules could be isolated from Xenopus thymocytes.