Anti-CD40L mAb treatment facilitates alloengraftment in a major mismatch transplant model that is augmented by CD45-ADC. B6 (H-2^b) recipients (10- to 12-week-old female) were conditioned with 3 mg/kg isotype-ADC or CD45-ADC on d-2 and 0 to 350 cGy (x = cGy in figure) TBI on d-1. All groups of mice were transplanted with 40 × 10⁶ BALB/c (H-2^d) BM cells on d0. Recipients were treated with anti-CD40L mAb (200 μg) from d-1 to d+14 post-BMT. (A) Engraftment of donor cells (H-2^d) in the PB of transplanted mice were analyzed at 4 weeks, 8 weeks, and 12 weeks post-BMT by flow cytometry (n = 8 to 22 mice per group). (B) Multilineage peripheral donor chimerism was analyzed at 12 weeks post-BMT by flow cytometry (n = 8 to 22 mice per group). (A,B) Data represent mean ± SEM. *P < .05, **P < .01, ***P < .001, ****P < .0001, 2-tailed Student t test. Pooled data from 2 to 3 experiments are shown.