Antibody-mediated engagement of β1-integrins.

Antibody-mediated engagement of β1-integrins inhibits S-phase entry of cultured blood CFC. Mobilized PB CD34⁺ cells cultured for 48 hours in serum-free medium with low-dose cytokines were incubated with adhesion-blocking antibodies against the α2 (n = 3), α4 (n = 6), α5 (n = 5), or β1 (n = 6) integrins or CD62L (n = 3) or mouse IgG (n = 6). After incubation for 30 minutes at 4°C, cells were washed and incubated with goat antimouse antibody. Cells were incubated for 8 to 12 hours at 37°C, and the percentage of CFC in S phase was assessed by thymidine suicide assay. Data are shown as the mean ± SEM. Comparison between anti-β1, anti-α4b and anti-α5 group and IgG control group: * = P < .01.