CXCL7 peptides and megakaryocyte colony growth. (A) G-CSF–mobilized CD34⁺ cells were cultured in serum-free culture media using the Megac-ult-C kit (Stem Cell Technologies), fixed, stained after 10 to 14 days with anti-CD41 antibodies, and scored for colony number and size (small colonies had 3-20 cells, medium 21-50, and large more than 50 cells), all per the manufacturer's instructions. Results are shown as a percentage of control colonies. Colony numbers were significantly smaller than control colony numbers when NAP-2 was added at concentrations of either 50 ng/mL (P = .010) or 100 ng/mL (P = .018). Colony numbers were not affected by LDGF or β-TG. (B) Percentage of CFU-Meg colonies larger than 20 cells in the same assays as in panel A. NAP-2 significantly decreases the size of the colonies at concentrations of 50 ng/mL and 100 ng/mL (P values of .001 and .006, respectively). For the CFU-Meg assays, G-CSF–mobilized CD34⁺ cells from 4 different donors were plated in duplicate sets. Results shown are mean values ± SE. P values were calculated using Student t test.