Host B cells inhibit donor cellular expansion and engraftment. Bone marrow and T cells from allogeneic Balb/c donors were transplanted into lethally irradiated μMT (n = 8) and wild-type (n = 8) recipient mice. Non-GVHD wild-type (n = 4) and μMT (n = 4) controls received BM and T cells from syngeneic or TCD allogeneic donors. Splenocytes were phenotyped on day 10 after transplantation. (A) Absolute numbers of each cell lineage. Results represent mean ± SE of individual animals. (B) Relative proportions of donor engraftment as described in “FACS and cytokine analysis.” Results represent mean ± SE of individual animals. *P < .05 versus respective wild-type groups. NS indicates not significant.