The role of integrin α6 and α4 receptors for homing of fetal liver progenitors to BM and spleen. FL cells were injected into lethally irradiated recipient mice. Three hours after injection, cells from blood, BM, and spleen were collected for CFU-GM assay. Data are pooled from 3 independent experiments. (A) Percentages of injected FL HPCs (GFU-GM) from integrin α6^−/− FL (α6^−/−) embryos and wild-type littermates (α6^+/+) recovered in blood, BM, and spleen. (B) Frequency of CFU-GMs in integrin α6^−/− and wild-type (α6^+/+) FLs. (C) Percentages of FL CFU-GMs recovered in blood, BM, and spleen after treatment with a function-blocking antibody against integrin α6 receptor (α6) or isotype control antibody (rIgG). (D) Frequency of CFU-GMs in FL cells cultured after treatment with the antibody against integrin α6 receptor (α6) or isotype control antibody (rIgG), or without pretreatment with antibodies (no ab). (E) Percentages of FL CFU-GMs recovered in blood, BM, and spleen after treatment with a function-blocking antibody against integrin α4 receptor (α4) or isotype control antibody (rIgG). (F) Frequency of CFU-GMs in FL cells cultured after treatment with the antibody against integrin α4 receptor (α4) or isotype control antibody (rIgG), or without pretreatment with antibodies (no ab). The results in panels C and E are pooled from 2 separate experiments. *P < .05, **P < .01, ***P < .001, compared with results obtained from wild-type FL cells (A,B) or cells treated with the isotype control antibodies (C-F). Each dot represents mean of 2 duplicate measurements from one recipient mouse. The horizontal bars show mean values.