Increased expression of Fcγ receptors on neutrophils and monocytes may reflect ongoing bacterial infection

The FcγR receptors for IgG, FcγRI, FcγRII and FcγRIII were measured on neutrophils and monocytes from 36 patients suspected of systemic infection, These results were compared with 30 blood donor controls to assess the level of expression as an early indicator of bacterial infection. FcγRT expression on neutrophils was found to be significantly increased from patients with systemic or localised infections, when compared to the non-infected patient group, i.e., patients with no cultural evidence of bacterial infections, (p=0.02, p=0.04) or normal controls (p<0.0001, p=0.0005). PcγRI expression on monocytes was also significantly increased in both of the infected groups compared to normal controls (p < 0.0001, p=0.001); however, no significant difference could be seen when compared with the non-infected patients. FcγRIII, was found to be significantly increased on a subset of monocytes in patients with systemic or localised infections compared to the non-infected group (p=0.009, p=0.006) and compared to the normal controls (p=0.009, p=0.003). Infections caused by gram-negative bacilli induced a higher FcγR response than infection with either streptococci or staphylococci. These data suggest that the measurement of FcγRI on neutrophils and FcyRIII on monocytes may be a useful rapid indicator of bacterial infection.