TREM1 and rheumatoid arthritis: When tested against the PMNs isolated from the inflamed synovia of RA patients, we found that these cells had an increased cytotoxic activity against these HTB-93 cells, compared to PMNs from normal specimens, corroborating that increased levels of activation through TREM1 correlate with the increased cytotoxic activity of PMNs from RA patients (Fig. 3B).