CD10+ stromal cells form B-lymphocyte maturation niches in the human bone marrow

In adult mammals, early B-lymphopoiesis takes place in the bone marrow in close association with stromal cells. Both the phenotype of the stromal cells and the molecules involved in this essential interaction are as yet inadequately described. In this study, all benign, differentiating B-cells (Pax-5+ lymphoid cells) are shown, by using two-colour immunohistochemistry on biopsies from human bone marrow, to be in close contact with scant dendritic CD10+ stromal cells until they leave via the sinusoids. This CD10+ stromal cell population does not fully overlap with the VCAM-1+ stromal cell population. Furthermore, using a set of B-cell differentiation markers (TdT, Pax-5, and CD20), B-cell development is shown to be spatially oriented, with maturation progressing towards bone marrow sinusoids. In conclusion, CD10+ stromal cells form distinct B-lymphocyte maturation niches in the human bone marrow.