Comparative influence of blood-borne nonbacterial particles and Staphylococcus aureus on fibronectin, complement and immunoglobulin.

Opsonic fibronectin deficiency has been documented in septic injured patients and suspected to reflect acute depletion due to blood-borne nonbacterial particulates. In the present study, the comparative effect of intravenous infusion of heat-killed Staphylococcus aureus or gelatin-coated nonbacterial test particles on immunoreactive fibronectin, IgG and C3 was investigated. These two test particles were selected because of their known dependence upon adequate opsonization for efficient RES phagocytic removal. The intravenous injection of gelatin-coated RE test lipid emulsion (50 mg/100 gm body weight) resulted in an acute depletion of serum fibronectin with no major alteration in circulating IgG or C3. This selective depletion of fibronectin was followed by a rapid restoration and elevation of fibronectin level within 24 hours. In contrast, intravenous infusion of heat-killed S. aureus (1 X 10 11/rat) resulted in an acute depletion of fibronectin and C2 within 60 minutes. The deficiency of these opsonic proteins after bacterial challenge was followed by elevation of fibronectin and normalization of C2. IgG was not significantly changed at any time. The decline in fibronectin and C3 was greater with an increase in bacterial dose. These studies emphasize the specificity of the opsonic deficiency induced by gelatin-coated particles. Additionally, the suggest that opsonic deficiency with S. aureus bacteremia may be, in part, functionally related to disturbances of fibronectin. The role of fibronectin deficiency in documented states of opsonic deficiency with sepsis warrants consideration.