Evidence for splenic suppressor cells in C3H/He, T-cell-deprived C3H/He, and nude mice bearing a 3-methylcholanthrene-induced fibrosarcoma.

Suppressor cells were demonstrated in the spleens of C3H/He mice carrying 3-methylcholantrene-induced fibrosarcomas. These cells inhibited the in vitro reactivity of normal lymphocytes to T- and B-cell mitogens. They disappeared within a few days after the tumor was surgically removed. Pretreatment of spleen cells (ScC) from tumor-bearing (TB) mice with either iron and a nagnet, antiserum against Thy 1.2 antigen plus complement, or antiserum against immunoglobulin plus complement demonstrated that the suppressor cells were adherent, non-T-cells bearing immunoglobulin at their surfaces. The suppressive effect could still be demonstrated by addition of SpC from TB mice 24 or 48 hours after phytohemagglutinin stimulation of normal SpC, SpC from TB C3H/He mice inhibited mitogen-induced stimulation of both C3H/He and DBA/2 lymphocytes. In T-cell-deprived TB C3H/He mice, suppressor cells were also observed and had the same characteristics as those in non-T-cell-deprived mice. In nude mice, however, although suppressor cells were active, they were not adherent and did not bear immunoglobulin at their surfaces. The existence of these suppressor cells may be one reason why the immune system of TB animals is unable to reject the tumor.