The effect of lactoferrin, an iron-binding protein on complement activity

ABSTRACT

The effect of Lactoferrin (LF) on complement activity has been studied using the sheep red blood cell - haemolysin system. Although Lactoferrin itself is devoid of complement activity, it does affect complement action. In the absence of 2 C50 units of complement, lysis occurs, the amount observed depending on the ratio of complement to Lactoferrin used. C1 was shown to be the target for Lactoferrin action, since the inhibition of lysis produced by 500 ug of Lactoferrin, could be completely reversed by crude C1.C3, a contaminant of this crude preparation, had no such effect. Investigations to establish the specific effect of Lactoferrin on C1 indicate that Lactoferrin is a potent activator of C1, since a six-fold increase in C1 activity results when they are mixed together. These observations are consistent with the hypothesis, that Lactoferrin exerts an influence on the complement system, as a result of its capacity to activate C1. (AU)