Breastfeeding-mediated tolerogenic NIMA effect is dependent on CD4⁺CD25⁺ cells. A newborn B6 mouse was fed by either a B6 mother (control) or a B6D2F1 foster mother (NIMA-b/d). (A) CD4⁺ T cells (10⁶) isolated from spleens of NIMA-b/d mice or controls were adoptively transferred into irradiated B6D2F1 mice. Numbers of IFN-γ⁺ donor CD4⁺ T cells in spleens 5 days after the transfer are shown as mean plus or minus SD (n = 5/group). (B,C) Lethally irradiated B6D2F1 mice received a transplant of 5 × 10⁶ TCD-BM from control B6 mice together with 2 × 10⁶ T cells from NIMA-b/d, controls, or syngeneic B6D2F1 donors. Survival after BMT (B; n = 11/group) and numbers of double-positive thymocytes at 40 days after BMT (C) are shown. (D) B6D2F1 mice received a transplant as described for panels B and C with T cells from a B6 mouse fed by either a B6D2F1 (NIMA-b/d) or B6D1F1 (NIMA-b/q) foster mother. Survival after BMT is shown (n = 14 /group). (E) BMT was performed as described for panels B and C with 0.5 × 10⁶ CD25-depleted CD4⁺ T cells from NIMA-b/d or control donors. Survival after BMT is shown (n = 10 /group). (F,G) Newborn B6 mice were nursed by a B6D2F1 mother and subcutaneously injected with 75 μg/g body weight of anti-CD25 or irrelevant mAbs 1 and 8 days after birth. The numbers of Foxp3⁺CD4⁺CD25⁺ cells in spleens at 3 and 8 weeks after birth (n = 3/group, mean ± SD; F) and survival of B6D2F1 mice that received a transplant of CD4⁺ T cells from anti-CD25–treated or control-treated NIMA-b/d donors or B6 donors (G) are shown (n = 11/group). (A,F) The results are representative of 3 replicate experiments. (B-E,G) Data from 2 similar experiments are combined. *P < .05; **P < .01 versus controls.