Mouse immunoglobulin receptors on lymphocytes: identification of IgM and IgD molecules by tryptic cleavage and a postulated role for cell surface IgD

Abstract

The 2 mouse immunoglobulin [Ig] receptors on lymphocytes (IgM and IgD-like) were individually digested by trypsin. Their trypic susceptibility and the products released were similar to those of their human counterparts. Evidence for a structural homology between human IgD and its presumed mouse counterpart was provided by the remarkably similar profile of fragments resulting from digestion. The extreme susceptibility of surface IgD to proteolysis contrasted with the resistance of surface IgM. The major role of IgD is to release a fragment (Fab.delta.) following exposure to antigen, and then elicit a regulatory anti-idiotype response which acts through recognition of the protease-resistant IgM idiotype remaining on the cell surface.