In vitro induction of suppressor T-cells in delayed-type hypersensitivity to BCG and an essential role of I-J positive accessory cells.

Antigen-specific suppressor T-cells in delayed-type hypersensitivity (DTH) to BCG were induced in vitro. Normal spleen cells of C3H/He mice were incubated with 50 micrograms of PPD per ml for 4 days at 37 degrees C, and the non-adherent cells in the culture were transferred intravenously into cyclophosphamide (CY)-treated syngeneic recipients. The recipients were immunized to BCG immediately after the cell transfer, and DTH was measured by the footpad reaction to PPD two weeks later. Footpad reaction to PPD was positive in CY-treated C3H/He mice immunized to BCG, while it was suppressed by the transfer of the in vitro induced suppressor cells. When the suppressor cells were treated with anti-thy-1.2 antiserum and complement before transfer, the suppression was abrogated. Next, the spleen cells were separated into plastic adherent and non-adherent fractions. After treatment with anti-thy-1.2 and complement, the adherent cells were treated with either anti-I-Jk or anti-I-Ak antiserum and complement. Then, they were reconstituted with the non-adherent cells and cultured with PPD. Treatment of the adherent cells with anti-I-Jk antiserum and complement abrogated the suppressor cell induction, while the treatment with anti-I-Ak had no effect. These facts indicate that I-J positive non-T-adherent cells play an essential role in the induction of suppressor cells in DTH.