ACP5 and Arthritis: Treatment of PBMC with macrophage colony-stimulating factor (M-CSF) alone (unstimulated control) showed similar initial values of tartrate-resistant acid phosphatase (TRAP) activity in both arthritis (group A) and Charcot patients (group C), with slightly elevated values in the latter (range from 3.166 to 4.477 for group A (median 3.767 mU) and from 3.531 to 7.136 for group C (median 4.829 mU); Figure 1A).