Effect of cytokines on the expression of RANK-L, OPG, RANK, and TRAF6 mRNAs by normal human blood neutrophils in vitro. Purified neutrophils were incubated in control medium (CM) or in survival medium (SM) for 1 to 3 days (D1, D2, D3). After RNA extraction, semi-quantitative reverse transcriptase-polymerase chain reaction analysis was performed. Histograms represent mean ± standard error of the mean of ratios of densitometric values for RANK-L/β-actin, OPG/β-actin, RANK/β-actin, and TRAF6/β-actin (n = 5 normal donors). Student's paired t test: *p < 0.05 (D3 versus D1, D2 versus D1). OPG, osteoprotegerin; RANK, receptor activator of nuclear factor-kappa-B; RANK-L, ligand of receptor activator of nuclear factor-kappa-B; TRAF6, tumor necrosis factor receptor-associated factor 6.