Flow cytometric analysis of BM cells from wild-type (WT) and Postn^−/− mice. BM cells from 16-week-old mice were analyzed for the expression of B220 and for CD43 (left) and for surface IgM and CD43 within the B220⁺ population (right). Numbers indicate the percentages of various lymphocyte stages: pre indicates pre-B stage; and pro, pro-B stage. Similar results were obtained in ≥ 3 separate experiments and also with BM of 3-week-old mice; a total of 10 mice were examined.