Role of VLA-4 and VLA-5 in mediating adhesion and transmigration of CD34⁺ cells in different phases of the cell cycle.

(A) Migration of cultured CD34⁺ cells toward MS-5 CM was assayed in Fn-coated transwells during 3 hours, after which cell cycle status of nonmigrating and migrating cells was determined by PI staining. Prior to transmigration, cells were incubated with blocking antibodies against VLA-4 or VLA-5 integrins. Control cells were treated with isotype-matched control IgG. Percent inhibition of migration was calculated for cells in G₀/G₁, S, and G₂/M (n = 5). *Inhibition by anti–VLA-5 was lower in G₂/M cells compared with S or G₀/G₁cells (P < .05). (B) Adhesion of cultured CD34⁺ cells to Fn was measured after neutralization of VLA-4 or VLA-5 by blocking antibodies or incubation with control IgG. After 1-hour adhesion, the cell cycle status of adherent and nonadherent cells was determined by PI staining. Data represent the percent inhibition of Fn binding compared with control IgG in each phase of the cell cycle (n = 4). *Inhibition of Fn binding by anti–VLA-4 was lower in G₂/M compared with S and G₀/G₁ cells (P < .05). **Inhibition of Fn binding by anti–VLA-5 was lower in G₀/G₁ compared with S and G₂/M (P < .05).