Response to PHZ-induced erythroid stress in β₁-, α₄- and VCAM-1-deficient mice. Control (n = 23), β₁^Δ/Δ (n = 6), α₄^Δ/Δ (n = 8), and VCAM-1^Δ/Δ (n = 5) mice were subjected to PHZ challenge and killed on day 6. (A) BM and (B-C) splenic responses were assessed in terms of cellularity and progenitor content (left panels) or erythroid differentiation (right panels). #Significant difference over the corresponding control (P < .05). Note that erythroblast maturation defects were not present in VCAM-1^Δ/Δ mice.