Effect of neutralizing anti–IL-8 or anti-CXCR1/anti-CXCR2 antibodies on the maturation of megakaryocytic cells derived from MMM CD34⁺ cells. Purified CD34⁺ cells from MMM and healthy subjects (NPB) were cultured for 14 days in serum-free medium containing a cytokine cocktail (9F or MK medium) in the absence or presence of neutralizing anti–IL-8 (panel A) or anti-CXCR1 or anti-CXCR2 (panel B) antibodies. The cells were cytocentrifuged and stained with May-Grünwald-Giemsa (magnification × 400). In panel B, the asterisk indicates the presence of MK cells with plump lobulated nucleus in MMM untreated cells, and the black arrow designates MK cells with polylobulated nucleus in the anti–IL-8– or anti-CXCR1 antibody–treated cultures in patients with MMM. Similar polylobulated nuclei were also obtained in anti-CXCR2 antibody–treated MMM cultures.