Alternate complement pathway activation by recluse spider venom.

Venom from the poisonous brown recluse spider (Loxosceles reclusa) catalyses the lysis of dithiothreitol-treated human erythrocytes when incubated with serum complement but not in heat inactivated serum, a characteristic of complement system activation via the alternate pathway. This activity of the venom was shown to reside in a Sephadex G-75 fraction of the venom which also contains the dermonecrotoxin. Isoelectric focusing of this fraction identified the complement inactivating molecules(s) in the region near pH=6. Analysis of complement after interaction with venom indicated a loss of haemolytic C3. Immunoelectrophoretic development of venom-complement mixtures with anti C3 proactivator revealed the appearance of the C3 activator. These data indicate that recluse spider venom activates the alternate complement pathway.