Density differences between membrane and secreted immunoglobulins of murine splenocytes

Abstract

The buoyant densities of mouse immunoglobulins [Ig] were determiend by isopyenic centrifugation in phosphate-buffered CsCl using .beta.-galactosidase as marker. The buoyant densities of IgG, TEPC 15 IgA, secreted IgM and MOPC 104E IgM were consistent with their carbohydrate contents in the presence and the absence of the nonionic detergent, Nonidet P-40. Intracellular IgM from spleen cell lysates had a buoyant density corresponding to a carbohydrate content of 6%. Membrane IgM from detergent lysates of spleen cells was less dense than intracellular or secreted IgM in the presence of detergent. The IgD-like membrane molecules were more dense than membrane IgM.