Development of cytotoxic T-cell activity in CBA mice after adoptive transfer of CD4⁺ T cells from naive CBA mice or CBA mice tolerant to BALB/c H-2^d antigens.

(A) CTL activity to H-2^d–positive target cells in the adoptively transferred CBA mice after immunization with BALB/c PBMCs. (B) CTL activity to H-2^b–positive target cells in the adoptively transferred CBA mice after immunization with BL/6 PBMCs. (●), CBA mice without adoptive transfer treatment (positive control); (■), CBA mice transferred with 5 × 10⁶ spleen CD4⁺ T cells of naive CBA mice; (▵), CBA mice transferred with 5 × 10⁶ spleen CD4⁺ T cells from tolerant CBA mice; (○), naive CBA mice without any treatment (negative control).