Activation of the first component of complement evidence for an internal activation step.
D000818:Animals; D003169:Complement Inactivator Proteins; D003165:Complement System Proteins / Q000378:metabolism*; D004912:Erythrocytes / Q000276:immunology; D006168:Guinea Pigs; D006461:Hemolysis; D007106:Immune Sera; D012756:Sheep
D003169:Complement Inactivator Proteins; D007106:Immune Sera; D003165:Complement System Proteins