Figure 1. CD4–B cell interactions following lymphoablation occur independently of MHCII expression on B cells and specific antigen recognition.

(A) Proposed model. (B) Lethally irradiated B cell–deficient μMT mice received a 1:1 mixture of μMT plus WT (control) or μMT plus MHCII^−/− (B cells lacking MHC class II) bone marrow (BM). Resulting BM chimeras received BALB/c heart allografts and were treated with mATG (1 mg i.p. on days 0 and 4). Percentages of CD4⁺ and CD8⁺ among peripheral blood live cells were determined by flow cytometry. (C) Mar TCR-transgenic T cells (CD4⁺, HY-reactive) were transferred into male or female C57BL/6J mice followed by BALB/c heart transplantation and mATG treatment. Results are representative of 2 experiments with n = 3–5 animals/group/experiment; error bars represent SD. *P < 0.05; ns, P ≥ 0.05 by multiple t tests.