IgM anti-IgM cold lymphocytotoxins to B cells

Cytotoxic antibodies to B lymphocytes have been shown to be IgM. They are not absorbed by red blood cells and therefore not absorbed by red blood cells and therefore not directed against the I antigen of red cells. They are also not inhibited by mannose, as are certain natural cytotoxins against lymphocytes. Methods for producing purified eluates of IgM anti-IgM antibodies are given. These antibodies are postulated to be immunoregulative by acting on B lymphocytes.