Id2 knock-out mice show enhanced B-cell development and impaired erythroid development. (A-C) FACS analysis of hematopoietic lineages in Id2+/+ and Id2−/− BM, spleens, and thymuses. (D) BMCs (5 × 105) from Id2+/+ or Id2−/− mice (CD45.2) together with 5 × 105 BMCs from C57BL/6 (CD45.1) mice were transplanted into irradiated C57BL/6 (CD45.1) mice. B-cell and erythroid reconstitution were examined 4 months after transplantation by analyzing CD45.2-positive BMCs using B220, CD43, TER119, and CD71 antibodies. *P < .01.