Long-term multilineage repopulation of the blood system is enhanced by WSS. Rag2^−/− Il2rγ^−/− recipients received 16 e.e. of E9.5 PSp cultured in the presence of either static (<0.0001 dyn/cm²) or WSS (5 dyn/cm²) conditions for 36 h. (A) Donor contribution to recipient leukocytes in peripheral blood is distinguishable as a discrete CD45.2⁺ CD45.1⁻ population in WSS recipients (20-wk posttransplantation data shown). (B) Peripheral blood reconstitution is significantly greater from cells exposed to WSS (n = 17 static from six independent experiments, n = 15 WSS from seven independent experiments; two-way ANOVA: *, P = 0.03). (C) Representative flow cytometry plots from the WSS recipient in A show lineage⁺ engraftment from CD45.2⁺ donor–derived cells. (D) Lineages present in CD45.2⁺ donor peripheral blood from individual recipients at 5, 10, and 20 wk after transplantation. B lymphopoiesis and long-term multilineage potential are bolstered by WSS. (E) CD45.2⁺ donor PSps contribute to greater numbers of cells expressing B lineage markers during the posttransplant period (20 wk) when exposed to WSS (n = 17 static, n = 15 WSS; Mann–Whitney rank sum: *, P = 0.03). (F) Primary recipient bone marrow was analyzed at 20 wk after transplantation of cultured PSp with markers of B lineage maturation (two static and three WSS recipients are shown alongside adult donor strain). B cells within the bone marrow collected from WSS recipients resemble adult donor marrow. (G) Production of early and late B lineages in primary bone marrow was discriminated by B220 and CD43 cell surface expression in the CD45.2⁺ donor population. Early B lineage phenotypes were marginally elevated by WSS (B220⁺ CD43⁺: n = 3 static, n = 5 WSS; unpaired Student’s t test: *, P = 0.13). Data are represented as mean ± SEM.