Expression of CD64 on polymorphonuclear neutrophils in patients with familial Mediterranean fever.

Familial Mediterranean fever (FMF) is an autoinflammatory disease characterized by recurrent episodes of fever and serosal or synovial inflammation. We examined the utility of CD64 (FcγRI) expression in polymorphonuclear neutrophils (PMNs) as clinical and biological parameters in patients with FMF. We studied 12 Japanese FMF patients (mean age; 22·8 ± 15·5 years, male/female: 2/10), along with rheumatoid arthritis patients (RA, n = 38 male/female: 6/32, mean age; 52·2 ± 15·3 years), systemic lupus erythematosus (SLE, n = 15 male/female: 0/15, mean age; 38·5 ± 15·9 years) and 12 healthy subjects (male/female: 3/9, mean age; 37·9 ± 17·2 years). CD64 expression on PMNs was determined using flow cytometry. The quantitative expression of CD64 in patients with FMF (2439·6 ± 2215·8 molecules per PMN) was significantly higher than in healthy subjects (547·8 ± 229·5, P = 0·003) or in patients with RA (606·5 ± 228·2, P < 0·0001) and SLE (681·3 ± 281·1, P = 0·004). The increased CD64 expression on PMNs isolated from untreated FMF patients was down-regulated by colchicine treatment. NACHT-LRR-PYD-containing protein 3 (NLRP3) activation using MurNAc-L-Ala-D-isoGln (MDP) resulted in increased CD64 expression on PMNs from healthy subjects. Our results suggest that quantitative measurement of CD64 expression on PMNs can be a valuable tool to discriminate between FMF and autoimmune diseases.