Adding anti-CD40L mAb has variable efficacy in promoting fully allogeneic donor engraftment in Fancg^−/− recipients. A−F, Female or male Fancg^−/− (B6, H-2^b) mice (10- to 16-weeks-old) were conditioned with isotype-ADC (0.5 mg/kg) or CD45-ADC (0.5 or 1.5 mg/kg) on d2 and received 40 × 10⁶ BALB/c (H-2^d) donor BM cells on d0. ADC–conditioned Fancg^−/− recipients were also treated with anti-CD40L mAb per Figure 5. (A) Engraftment of donor cells (H-2^d) in the PB of mice who underwent transplant were analyzed at 5, 17, and 28 weeks post-BMT by flow cytometry, and multilineage peripheral donor chimerism was analyzed at 28 weeks post-BMT (B). (C-F) Recipients were killed at 29 weeks post-BMT, and donor (H-2^d) chimerism in BM (C,F), thymus (D), and spleen (E) were analyzed. (G-M) Female or male Fancg^−/− mice (10- to 16-weeks-old) were conditioned with isotype-ADC (0.5 mg/kg) plus anti-CD40L mAb or CD45-ADC (0.5 or 1.5 mg/kg) ± anti-CD40L mAb and received 40 × 10⁶ donor (H-2^d) BM cells as above. (G) Engraftment of donor cells (H-2^d) in the PB of mice who underwent transplant were analyzed at 5, 15, and 25 weeks post-BMT, and multilineage peripheral donor chimerism was analyzed (H) at 25 weeks post-BMT. (H) CD45-ADC (1.5 mg/kg) vs CD45-ADC (1.5 mg/kg) + anti-CD40L mAb; CD3 (P < .0001), CD11b (P = .0002). (I-M) Recipients were killed at 30 weeks post-BMT, and donor (H-2^d) chimerism in BM (I), thymus (J), and spleen (K) were analyzed. The frequencies of donor (H-2^d) effector/memory (CD44^hiCD62L^lo) T cells in spleen (L) and donor (H-2^d) Treg cells in thymus (M) were also analyzed at 30 weeks post-BMT by flow cytometry. For panels A-M, data represent mean ± SEM (n = 4-5 mice per group). ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, and ∗∗∗∗P < .0001 using the 2-tailed Student t test.