Modulation of CCR5 mRNA expression by salbutamol and/or pentoxifylline. (A) Monocytes were incubated for 4 hours with medium, salbutamol, pentoxifylline, or both drugs. Northern blot analysis of CCR5 mRNA expression is illustrated. (B) Cells were incubated with medium or the combination of pentoxifylline (ptx) and salbutamol (salbu) for the indicated time periods and CCR5 mRNA expression was analyzed by Northern blot. n = 2 to 4 independent experiments.