Increased expression of Fc gamma receptors on neutrophils and monocytes may reflect ongoing bacterial infection.

The Fc gammaR receptors for IgG, Fc gammaRI, Fc gammaRII and Fc gammaRIII 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. Fc gammaRI expression on neutrophils was found to be significantly increased from patients with systemic or localised infections, when compared to 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). Fc gammaRI 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. Fc gammaRIII 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 Fc gammaR response than infection with either streptococci or staphylococci. These data suggest that the measurement of Fc gammaRI on neutrophils and Fc gammaRIII on monocytes may be a useful rapid indicator of bacterial infection.