Figure 2

Increased osteoclast formation from splenocytes of interferon-γ receptor knock-out (IFN-γR KO) mice. Splenocytes of IFN-γR KO (KO) mice and wild-type (WT) mice were isolated. Mice were either naive or had been immunised with collagen type II in complete Freund's adjuvant 21 days previously. Cells were stimulated for 6 days in chamber slide cups with 20 ng/ml macrophage colony-stimulating factor (M-CSF) and 100 ng/ml receptor activator of NF-κB ligand (RANKL) (a) or 20 ng/ml M-CSF and 20 ng/ml tumour necrosis factor-α (TNF-α) (b). After stimulation, cultures were fixed and stained for the presence of tartrate-resistant acid phosphatase (TRAP). (a,b) TRAP⁺ multinucleated (three or more nuclei) cells were counted within each cup. In each group, bars represent averages ± standard error of the mean for five mice. *P < 0.05 compared with wild–type mice (Mann-Whitney U-test). (c,d) Representative pictures of TRAP-stained cultures of RANKL-stimulated IFN-γR KO (c) and wild-type (d) splenocytes. Insets show details of multinucleated TRAP⁺ cells. (e,f) Osteoclast activity after stimulation by RANKL of IFN-γR KO (e) and wild-type (f) splenocyte cultures, as analysed by their ability to resorb a calcium phosphate film coated on a quartz substrate. Sites of resorption are indicated by arrows. CIA, collagen-induced arthritis.