INFECTION WITH HUMAN CYTOMEGALOVIRUS (HCMV) STIMULATES MONOCYTE PRODUCTION OF COMPLEMENT FACTOR-3

Complement biosynthesis in monocytes is stimulated by different microo rganisms including Gram negative bacteria and yeasts. We have tested t he effect of human cytomegalovirus (HCMV) on complement factor 3 (C3) production by cultured human monocytes. The monocytes were challenged with either a crude or a purified HCMV preparation obtained from the s upernatant of HCMV-infected fibroblasts. When the monocytes were infec ted with 2 pfu/cell of virus and cultured for 2 days, the increase in C3 production compared to control ranged from 3% to 162%, median 62% ( p < 0.01). However, crude HCMV was even more potent in stimulating C3 production, as the increase in C3 values ranged fi-om 104% to 507%, me dian 247% (p = 0.001). This indicates the presence in the crude HCMV p reparation of a substance which acts synergistically with HCMV on the C3 production. When monocytes were stimulated by lipopolysaccharide (L PS), a well known inducer of C3, infection with crude or purified HCMV did not further increase C3 production. Both HCMV and substances prod uced during the propagation of HCMV in fibroblasts are able to stimula te C3 production in monocytes. Complement production by inflammatory c ells may be of importance in host resistance against viral infections.