Response to cytotoxic stress induced by 5FU in the absence of α4 integrin. Individual groups of Mx.cre+α4+/+ and Mx.cre+α4Δ/Δ mice (n = 4 per genotype) were treated with 5FU, and analyzed 4, 8, 12, or 16 days later to determine the level of myeloid recovery in the BM and PB (nucleated cells and progenitor cells). White bars, Mx.cre+α4+/+mice; black bars, Mx.cre+α4Δ/Δ mice.