Partial properdin deficiency.

The action of properdin in supporting complement consumption has been investigated in the serum from two individuals with partial properdin deficiency. Our studies are in agreement with those in which serum were artificially depleted of properdin in showing that serum deficient in properdin results in less C3 consumption in the presence of activators of both the alternative and classical complement pathways. Properdin deficiency did not lessen C3 consumption by C3NeF or CoF, confirming that properdin is not necessary for the action of these substances. Our findings indicate that partial properdin deficiency is innocuous but that complete absence of properdin may severely limit one's ability amplify complement activation.