BMMs (13.0 ± 0.6 × 104) from which CSF-1 had just been removed were cultured in RPMI/10% FBS, in the absence or presence of BCP (500 μg/ml) or CPPD (500 μg/ml). After one day, cells were washed twice to remove cystals and recultured in RPMI/10% FBS for a further two days. Then the number of viable cells was determined by hemocytometer counting and trypan blue exclusion. Data are mean values ± SEM from triplicate cultures and are from a representative experiment that was repeated once. aP < 0.05 in comparison with untreated group (Student's two-tailed t-test).