Multiple myeloma is often associated with humoral immunodepression in both man and mouse. When mice bearing the humorally immunodepressive plasmacytomas TEPC-183 and SPQC-11 were injected with SRBC, the rise of serum haemolysins was significantly less than that of non-tumour-bearing mice. Mice with the plasmacytomas MPC-11 and MOPC-315 have an antibody response similar to normal mice when injected with SRBC. Following immunization, normal mice and those bearing MPC-11 showed a 2- to 3-fold increase in total spleen lymphocytes. Mice bearing TEPC-183 or SPQC-11, the plasmacytomas causing an impaired antibody response, has significant increase in spleen lymphocytes under the same conditions. Mice bearing MOPC-315 had a very high initial count of spleen lymphocytes, which did not further increase upon immune stimulation
