Evidence for surface‐associated immunoglobulin on T and B lymphocytes

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Abstract
An electron microscopic study was carried out to characterize surface‐associated immunoglobulin on murine lymph cell populations. A panel of hybrid anti‐bodies with anti‐immunoglobulin and anti‐Southern Bean Mosaic Virus specificities permitted the identification of both κ and μ chain determinants on cell surfaces, indicating that surface‐associated immunoglobulin presumably represents IgM.The cells carrying immunoglobulin on their surface were identified as lymphocytes. In cell populations from lymph nodes 95 % of the mature lymphocytes possessed surface‐bound κ and μ determinants. This indicates that both thymus derived (T) and bone marrow‐derived (B) lymphocytes express IgM.Plasma cells do not carry immunoglobulin on the cell surface, which implies that antigen‐induced differentiation of B lymphocytes entails loss of surface IgM expression.In the thymus, surface‐associated immunoglobulin could not be detected on the vast majority (98 %) of the cells, but 2 % positive cells were found. T lymphocytes may thus acquire immunoglobulin as a surface constituent shortly before or after the cells leave the thymus.