Overview of the Complement System

These flashcards cover key terms and concepts related to the complement system, including activation mechanisms and pathway specifics.

Complement System

A group of more than 20 tightly regulated proteins that promote inflammation and eliminate invading pathogens.

Activation

The process by which complement proteins are activated from their inactive form in the circulation.

Alternate Pathway

Activated by the binding of C3 to bacterial cell-wall components such as lipopolysaccharide and teichoic acid.

Classical Pathway

Initiated when two or more IgM or IgG antibodies bind to an antigen, triggering the cascade via C1.

C1 Inhibitor (C1inh)

An important inhibitor of the classical pathway that prevents excessive complement activation.

Lectin Pathway

Activated when mannose-binding lectin interacts with microbial cell surface carbohydrates, stimulating the classical pathway.

C3

A central protein in the complement system that initiates the alternate pathway when bound to bacterial components.

Conformational Change

The alteration in the structure of antibodies upon binding to antigen, exposing binding sites for C1.