[Suppressor T cells against delayed type hypersensitivity to Mycobacterium intracellulare].

Mycobacterium intracellulare Mino strain (Mino) grows progressively in the organs of susceptible mice, such as C57BL/6, C57BL/10 or BALB/c. It is very difficult to induce acquired immunity against M. intracellulare in those susceptible mice. C57BL/6 (B6) mice show no or very weak delayed type hypersensitivity (DTH) to partially purified Mino antigens when sensitized with 10(7) living Mino subcutaneously. B6 mice pretreated with cyclophosphamide (CY) showed enhanced DTH to Mino, suggesting that suppressor mechanism exists in this system. Whether or not such a suppressor mechanism exists in the induction phase of DTH (A) and/or in the expression phase of DTH (B) was examined by cell transfer experiments. Recipients for testing (A) were B6 mice receiving CY 2 days before an immunization, and those for (B) were B6 mice receiving both CY and subcutaneous injections of Mino 3 weeks before the cell transfer. B6 mice which were intravenously injected with Mino a week or 6 weeks before preparing spleen cell suspension, were used as the donors. Single cell suspensions of the spleens were plated on tissue culture dishes and non-adherent cells were harvested after incubating for 60 min at 37 degrees C. These cells were used for cell transfer. In the induction phase experiment, recipient mice received the cells before sensitization, while they received the cells after sensitization in the expression phase experiment. DTH were markedly suppressed in the cell transferred groups as compared with the non-transferred groups. This activity disappeared by treatment of the transferred cells with antibody (alpha Thy-1 Ab) and complement.(ABSTRACT TRUNCATED AT 250 WORDS)