T and B lymphopoiesis are impaired in MT1-MMP^−/− mice. (A) PB B- and T-cell numbers (FACS analysis). (B) Images of mouse spleens. (C) H&E-stained spleen sections. Arrowheads indicate megakaryocytes (bars, 100 μm). (D-E) The (D) total number of splenocytes and (E) B220⁺ cells in splenocytes (n ≥ 6). (F) The percentage of B220⁺ populations in BMNCs (n = 6), splenocytes (n = 3), and PB cells (n = 2). (G) Thymocyte number (n = 4). (H) Images of thymi. (I) H&E-stained thymus sections. MR indicates medullar region (bars, 100 μm). (J) The percentage of thymic T-lineage subpopulations. (K-L) BM cells from MT1-MMP^+/+ and MT1-MMP^−/− mice were transplanted into wild-type animals (CD45.2). (K) The percentage of donor CD4⁺/CD8⁺ T and (L) B220⁺B cell lineage contribution of donor-derived cells in the PB 4 months after transplantation (n = 10/group). Errors in bar graphs are SEM; *P < .05, **P < .01.