HSC adhere to stromal cells in a JAM-B dependent manner. (A) Graph showing adhesion of nonactivated or PMA activated Lin^Neg progenitor cells to plastic support (PBS), coated recombinant soluble JAM-B (sol-JAM-B) or recombinant soluble JAM-C (sol-JAM-C). After 1 hour, adherent cells were detached and percentages of adherent LSK cells were determined and compared with the percentage of LSK cells in the input of Lin^Neg population. Results are expressed as percentage of adhesion. (B) Adhesion of the indicated subset to the bone marrow stromal cell line OP9 is shown. Purified Lin^Neg progenitor cells were left untreated (white bars) or pre-incubated with sol-JAM-B (black bars) before incubation with the OP9 cell monolayer. After 1 hour, adherent cells were detached and percentages of adherent cells determined. Results are representative of at least 3 independent experiments (***P < .001).