The effect of lactoferrin on complement mediated modulation of immune complex size

Earlier we showed that human lactoferrin is capable of inhibiting the complement-mediated lysis of antibody-coated erythrocytes due to an inhibition of the formation of the classical C3 convertase. In this report the effect of lactoferrin on complement mediated modulation of immune complex size was studied. Lactoferrin was shown to inhibit the complement-dependent solubilization of immune precipitates with kinetics resembling that seen by others using C2 deficient serum. Lactoferrin, however, did not affect the complement-dependent inhibition of immune precipitation. These findings confirm our earlier observations that lactoferrin has no effect on the activation of the very early complement components (C1 and C4), but inhibits C3 deposition on immune complexes which is a crucial mechanism in immune precipitate solubilization.