JAM-B expression on stromal cells is required for BM engraftment. (A) The graph shows the percentage of chimerism at different time after graft of jam-b^−/− or jam-b^+/+ CD45.2 BM cells into lethally irradiated recipient CD45.1 mice. jam-b^+/+ BM cells as well as jam-b^−/− BM cells are able to reconstitute recipient mice. (B) Graph showing the proportion of T (CD3⁺), B (CD19⁺) and myeloid (CD11b⁺) cells in the blood of recipient mice 19 weeks after engraftment with BM cells from the indicated donor. (C) Percentage of survival of jam-b^−/− or jam-b^+/+ mice lethally irradiated and grafted with CD45.1 LSK cells. Most of jam-b^−/− mice die after irradiation (square) whereas all control mice survive (circle). (D) The graph shows the percentage of chimerism 4 weeks after graft of CD45.1 LSK cells into control (white bars) or jam-b deficient recipient mice (black bar). Results obtained in the BM and in the blood are shown. Results are representative of at least 5 mice per group (*P < .05).