Non-specific regulatory mechanism of contact sensitivity: induction of macrophage-like suppressor cells and their factors with hapten-conjugated lymphoid cells.

The mechanisms of non-specific unresponsiveness to contact sensitivity (CS) induced with intravenous (i.v.) administration of oxazolone (Ox)-conjugated syngeneic spleen cells was investigated. Non-specific suppressor cells were found in spleen cells of mice which had been injected i.v. with Ox-conjugated cells 7 days before. These non-specific suppressor cells blocked the efferent stage of CS profoundly, i.e. inhibited the activity of effector cells for picryl chloride (PCl). Since these suppressor cells were plastic-adherent and resistant to treatment with anti-Thy 1.2 antibody and complement, they were considered to be macrophage-like. These suppressor cells released non-specific suppressor factor(s) (NSF) during culture for 1 hr without any antigenic triggering. Effector cells for PCl which were treated with NSF for 1 hr at 4 degrees lost their ability to transfer CS. NSF was easily absorbed by normal spleen cells. Furthermore, these NSF-treated spleen cells acquired the ability to inhibit the passive transfer of CS non-specifically. We also discussed the pathway for the induction of these macrophage-like suppressor cells.