Cell surface immunoglobulin. V. Release from murine splenic lymphocytes.

Turnover and release of cell surface Ig and secretion of total intracellular Ig has been studied in small lymphocytes from normal mouse spleen. The major findings to emerge are: (a) small lymphocytes secrete 8S IgM and IgG. A small portion of the 8S IgM, but virtually none of the IgG appears to have a cell surface phase. (b) Cell surface IgM is actively turned over with a half-life of 6-8 hr, and turnover can be accounted for by release into the incubation medium. Release is temperature dependent. (c) Released cell surface Ig is noncovalently bound to a fragment of plasma membrane. (d) H-2 antigens are not released during short-term incubation. Based on the above findings, we propose a model for the transport and release of both cell surface and conventionally secreted Ig.