ABSTRACT

Thispathwaywasoriginallydiscoveredwhenitwasdemonstratedthatayeastcellwall preparationcalledzymosancouldconsumeC3at37°Cwithoutaffectingtheconcentrationsof C1,C4,orC2molecules(17).Itprovidesanaturaldefencesystemagainstmicroorganisms andotherpathogensandoperatesindependentlyofnaturalantibodies.Therearesixserum proteinsthoughttobeimportantinthealternativepathwayofcomplementactivation(18),of whichthreemediateactivationandamplification(C3,factorB,andfactorD)andtheother three(properdin,factorH,andfactorI)mediatecontrolfunctions.