Surface immunoglobulins on Xenopus laevis lymphocytes

Abstract

Abstract o 1. The surface immunoglobulins (Ig) on Xenopus laevis lymphocytes have been studied by immunofluorescence. 2. 60–85% of the lymphocytes in adult peripheral blood possess surface Ig. In post-Stage 48 tadpoles the proportion of such cells varies between 35 and 45%, the proportion rising to the adult level in the immediate post-metamorphosis period. 3. The proportions of surface Ig-carrying lymphocytes in the spleen and other lymphomyeloid organs are similar to those in the blood at any given developmental stage. The thymus is an exception: in tadpoles some 47–55%, and in metamorphs 70–75% of the thymocytes have surface Ig; this figure declines to between 8 and 12% in the adult. 4. In all situations the surface Ig appears to be almost exclusively IgM; IgG only presents on 5% or less of the cells. On no cells are both IgM and IgG present together. 5. The surface Ig can be capped, and can be removed by limited papain proteolysis of the cell surface: subsequent to capping or proteolysis the Ig is regenerated. 6. The phylogenetic significance of these results is discussed in terms of B and T cell delineation and differentiation.