Alternative pathway

Definition

The alternative pathway is a component of the complement system that enhances the ability to clear pathogens and damaged cells from an organism. It is activated on microbial surfaces in the absence of antibodies.

5 Must Know Facts For Your Next Test

1. The alternative pathway does not require antibodies for activation.
2. It plays a crucial role in the innate immune response by directly targeting pathogens.
3. Factor B, Factor D, and properdin are key proteins involved in this pathway.
4. Activation occurs through the spontaneous hydrolysis of C3 into C3(H2O), which then binds to factor B.
5. The alternative pathway can amplify the response initiated by the classical and lectin pathways.

Review Questions

• What triggers the activation of the alternative pathway?
• Which key proteins are involved in the alternative pathway?
• How does the alternative pathway contribute to pathogen clearance?

Related terms

Complement System:

A part of the immune system that enhances the ability to clear microbes and damaged cells.

Classical Pathway:

An antibody-dependent pathway of complement activation.

Lectin Pathway:

A complement activation pathway triggered by mannose-binding lectins binding to microbial surfaces.