Effect of depletion of CD25⁺ cells on the negative regulatory activity of CD4⁺ T cells from the tolerant CBA mice.

(A) Each naive CBA mouse was treated with 2.5 × 10⁶spleen CD4⁺ T cells with or without depletion of CD25⁺ cells from naive or tolerant CBA mice. No CD4⁺ T cells were given to the CBA mice in the control group (Control). Thereafter, all CBA mice were challenged with BALB/c PBMCs, and the development of anti–H-2^d antibody was determined as described. Analysis of variance showed that only the mice treated with tolerant CD4⁺ T cells without depletion of CD25⁺ cells (Tol.CD4⁺ cells) had anti–H-2^d antibody activity significantly lower than in the other 4 groups (P < .04). Anti–H-2^dantibody activities in the CBA mice treated with tolerant CD4⁺ with depletion of CD25⁺ T cells (CD4⁺/CD25⁻) were not significantly different than in the control and in those treated with naive CD4⁺with or without depletion of CD25⁺ T cells (P ≥ .40). There were 4 mice in each group. (B) In a separate experiment, each naive CBA mouse was adoptively transferred with 5 × 10⁶ spleen CD4⁺ T cells with or without depletion of CD25⁺ cells from naive CBA mice or CBA mice tolerant to BALB/c H-2^d antigens. Adoptively transferred and control CBA mice were challenged with H-2^b–positive BL/6 PBMCs, as described. Analysis of variance showed that only CBA mice adoptively transferred with the tolerant CD4⁺ T cells (Tol. CD4⁺ cells) developed anti–H-2^b antibody activities significantly lower than in the other 3 groups (P ≤ .02). There were 4 mice in each group.