Immune regulation of mouse 5T2 multiple myeloma. I. Immune response to 5T2 MM idiotype.

The transplantable murine multiple myelomas (MM) of the 5T series originated spontaneously in the aging C57BL/KaLwRij mice. These murine malignancies offer an excellent model for experimental studies on different aspects of the human disease. With the aim to look for new treatment modalities, the influence of idiotype-specific immune response on the 'take' and the development of the 5T2 MM was studied. In the first experiment, long-lasting subcutaneous immunizations of syngeneic mice with the 5T2 MM immunoglobulin (Ig) showed a dose dependent anti 5T2 MM Ig idiotype-specific response. The majority of the optimally immunized mice showed no 'take' or they had a prolonged survival after intravenous inoculation with the 5T2 MM cells. All control mice, nonimmunized or immunized with an irrelevant 5T14 MM Ig, developed 5T2 MM with a typical lethal course. In the second experiment, delayed type hypersensitivity (DTH) reaction to the 5T2 MM idiotype was studied. Subcutaneous immunizations of syngeneic mice with 5T2 MM Ig or with 5T2 MM bone marrow cells resulted in a specific DTH reaction 48 hours after challenge with 5T2 MM bone marrow cells. No DTH reaction was obtained when intravenous immunization was used. These results indicate that 5T2 MM is sensitive to idiotype-specific immune regulation; they constitute a basis for further studies on treatment of already established MM in vivo.