Changes in the haemolytic activity of bovine serum complement by Hypoderma lineatum (insect oestridae) larval proteinases in naive and immune cattle

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Abstract
Three serine proteinases (hypodermin A, B and C) of the 1st instar larvae of H. lineatum have been assayed for their ability to deplete seric complement of naive or immune cattle. In naive cattle complement consumption is initiated by hypodermin B through the sequence [complement component] C1-C3 at a concentration of 5 .mu.g/ml of serum, and by hypodermin A through the sequence of C3-C9 at a higher concentration of 150 .mu.g. The 3rd enzyme presenting a collagenolytic activity has no anticomplementary activity even on C1q. In immune cattle a 70% complement depletion through the classical pathway is observed with 15 .mu.g of hypodermin B/ml of serum. The 2 enzymes A and C appear to play a minor role in the complement depletion via the classical pathway. The biological role of each of these enzymes in the parasite-host interrelationships is discussed. The participation of these enzymes in the immediate hypersensitive reactions following systemic treatment of cattle infested by this endoparasite is considered.