Suppression of mitogen responses and graft-versus-host reaction by splenocytes from mice bearing Lewis lung carcinoma.

The presence of suppressor cells in the spleens of C57BL/6 mice bearing Lewis lung carcinoma was investigated with the use of the in vitro lymphoproliferative response to mitogens and the graft-versus-host reaction (GVHR) as test systems. Splenocytes from tumor-bearing mice showed a lower response to mitogens when obtained 15-27 days after tumor transplant. In parallel, these cells were capable of suppressing the response of normal spleen cells to mitogens and their capacity to mount a GVHR in allogeneic hosts. Treatments with procedures known to remove adherent phagocytes, but not treatments with anti-Thy 1.2 serum plus complement, removed the suppressive activity observed.