The ____________ cascade of complement activation is initiated by antibodies. In contrast, the ____________ cascade is activated by a direct interaction with complement proteins, and the ____________ cascade is activated by MBL associating with a pathogen.

Verified step by step guidance

1. Identify the three pathways of complement activation: classical, alternative, and lectin.
2. Understand that the classical pathway is initiated by antibodies binding to antigens on the pathogen surface.
3. Recognize that the alternative pathway is activated by direct interaction of complement proteins with pathogen surfaces, independent of antibodies.
4. Know that the lectin pathway is triggered when mannose-binding lectin (MBL) binds to carbohydrates on the pathogen surface.
5. Fill in the blanks with the appropriate pathways: classical, alternative, and lectin.

Key Concepts

Classical Pathway of Complement Activation

The classical pathway of complement activation is triggered by the binding of antibodies to antigens on the surface of pathogens. This pathway involves a series of protein interactions that lead to the opsonization of pathogens, recruitment of inflammatory cells, and formation of the membrane attack complex, ultimately aiding in the destruction of the pathogen.

Alternative Pathway of Complement Activation

The alternative pathway is activated through direct interactions between complement proteins and pathogen surfaces, independent of antibodies. This pathway serves as a first line of defense, providing rapid response to infections by amplifying the complement response and enhancing opsonization and inflammation.

Lectin Pathway of Complement Activation

The lectin pathway is initiated when mannose-binding lectin (MBL) binds to specific carbohydrates on the surface of pathogens. This pathway activates complement proteins similarly to the classical pathway, leading to opsonization and pathogen clearance, and is particularly important in the immune response to fungal and bacterial infections.