FIG. 4.

Response to PHZ-induced anemia in the absence of α4 integrin. Responses to hemolytic anemia were tested in Mx.cre⁺α4^+/+ and Mx.cre⁺α4^Δ/Δ mice (n = 4 per genotype) by PB differential analyses performed 2, 4, 6, 8, and 10 days after PHZ treatment. (A) Reduced reticulocyte levels were observed in the PB of the deletion-induced mice 4 to 6 days after PHZ administration. The α4 integrin-deficient platelet levels also failed to increase above baseline levels in response to PHZ from days 2 to 6. *, significant difference. White bars, Mx.cre⁺α4^+/+ mice; black bars, Mx.cre⁺α4^Δ/Δ mice. (B) Erythroid progenitor numbers in BM and spleen were evaluated 2 days after the last PHZ treatment by using plasma clot assays. BFU-e numbers were significantly reduced in the BM and spleen of deletion-induced animals. In contrast, CFU-e levels were reduced in the BM but not in the spleen.