Capping and Co‐Capping of Membrane Immunoglobulin and Lipid‐Conjugated Immunoglobulin Inserted in the Cell Membrane of B Lymphocytes

Human and mouse immunoglobulins (Ig) or F(ab′) 2 fragments of rabbit Ig were conjugated to lipids and the conjugates inserted into the membrane of mouse spleen cells. It was found that nearly all B cells, but not T cells, became decorated with lipid Immunoglobulin. Both endogenous Ig receptors and inserted Ig capped after the addition of cross‐linking F(ab′) 2 antibodies and in both cases capping required energy. Capping of endogenous mouse Ig led to co‐capping of inserted human Ig, but the reverse was not true.