Participation of the humoral immune system in the myeloma-specific transplantation resistance.

Studies are reported that examine the participation of humoral and cellular responses in the myeloma-specific transplantation resistance induced by preimmunization of BALB/c mice with purified myeloma protein M315. A plasmacytoma spleen colony-forming assay was used to provide a quantitative estimate of the tumor immunity in recipients of unfractionated spleen cells or serum from mice immunized four to seven times with M315. The primary findings were: 1) that the tumor immunity can be transferred by immune spleen cells provided that a boost of M315 is given to adoptive hosts, and 2) that passively transferred serum containing anti-M315 idiotype antibody (a-Id315) can also inhibit tumor growth. Adoptive transfer was successful in the presence of minute amounts of a-Id315, whereas passive transfer required relatively large amounts of activity. The passive transfer experiments involved an extended injection schedule and thus could not discriminate between direct effects of antibody or idiotype-specific humoral substances on tumor cells or inductive effects on the cellular immune system. Experiments examining the properties of the immune elements involved in the transplantation immunity demonstrated that, once established, they are resistant to acute radiation (to 800 R) and cortisone damage.