Complement System

Complement System

Complement System

Complement is a thermolabile (inactivated at 56° C, in 30 minutes) complex of eleven proteins present in the sera of most warm-blooded animals. By itself complement has little or no antimicrobial power, but it aids and complements the action of various types of antibodies. Complement proteins are designated by letter C and by number C1, C2 . . . C9. C1 consists of subunits C1q, C1r, C1s. These proteins react in an ordered sequence (C1q, C1r, C1s, C4, C2, C3, C5, C6, C7, C8, C9). That is, they cascade and function as immune effectors of the acute inflammatory response. When complements become activated, the various components function in sequence, proceeding from left to right through the above list.

During sequential activation of complement a number of biologic events are initiated which facilitate the localization and destruction of foreign material by immune effector cells. For some immunologic reactions all components are activated, while for others, the activation may stop at C3,C5,etc. The cations Ca++ and Mg++ are necessary for almost all functions of complement. The complement system can be activated by two pathways, the classical pathway and the properdin pathway.

Home | Site map | Submit Article | Directory | Search