Enrichment of suppressor cell activity by hydrocortisone: suppression of in vitro activation of splenocytes from mice bearing Lewis lung carcinoma.

Suppressor cells in spleens of mice bearing the Lewis lung carcinoma (3LL) suppressed the anti-tumor immune response in vivo but not in vitro. The hydrocortisone (HC)-resistant fraction of spleen cells from tumor-bearing mice (TBM) was, on the other hand, suppressive in vitro, due to enrichment for HC-resistant suppressor cells. This cellular fraction suppressed the tumor-induced differentiation of memory cells as well as the tumor-independent in vitro activation of TBM spleen cells. The in vitro lymphoproliferative response of TBM spleen cells to mitogens was also subjected to suppression: these cells showed a lower response to a mitogen such as Concanavalin A (Con A) and were capable of suppressing the response of normal spleen cells to this mitogen. HC treatment of TBM 2 days prior to spleen harvest enriched the splenic population for suppressor cells that suppressed Con A-induced activation.