Humoral immunosuppressive substance in mice bearing plasmacytomas.

The mechanism by which plasmacytomas (PC) depress the primary immune response to sheep red cells was investigated by determining the ability of normal spleen cells to produce antibody when enclosed in Millipore chambers and implanted in PC-bearing mice. Chamber-enclosed normal spleen cells implanted in PC-bearing mice responded poorly to the sheep red cells when compared to similar cells enclosed in chambers and implanted in normal mice or in mice with other lymphoid and nonlymphoid tumors. The data suggest that PC-induced immune suppression is mediated by a humoral factor.