Expression of receptors on bone marrow cell populations. (a) C5aR, CXCR1, CXCR2, CCR2 expression, and fluorescein isothiocyanate (FITC) LukS-Panton–Valentine leucocidin (PVL) binding on bone marrow leucocyte surface. Expression levels were assessed by the ratio of the median fluorescence intensity of a specific monoclonal antibody/median fluorescence intensity of the control (RMFI). RMFI ≥ 2 indicated that the population expressed the receptor. (b) C5aR expression on the granulocytic myeloid-derived cells and CD11b+ monocytes. (c) CXCR1 expression on the granulocytic myeloid-derived cells and CD11b+ monocytes. (d) FITC LukS-PVL binding on the granulocytic myeloid-derived cells and CD11b+ monocytes. Cell imm, immature cells; Gr imm 1, granulocytic immature 1 cells; Gr imm 2, granulocytic immature 2 cells; PMN, polymorphonuclear neutrophil cells; CD11b+ mo, CD11b+ monocytes; LyB CD19+, CD19 B lymphocytes; Ly T CD3+, T lymphocytes; NK, natural killer; T NK, T natural killer. The mean value of 11 bone marrows is shown; error bars correspond to standard deviation. Comparisons made using Student’s t-test with Bonferroni adjustment, *** p < 0.001; NS, non-significant.