The Complement System

These flashcards cover key terms and concepts related to the complement system from the lecture.

Complement System

A set of serum proteins that cooperates with innate and adaptive immunity to eliminate pathogens.

Complement Activation

The process involving pathways that activate complement proteins to function in immune response.

Opsonization

The process of marking pathogens for phagocytosis by binding antibodies or complement proteins.

Membrane Attack Complex (MAC)

A structure formed by complement proteins that creates pores in microbial membranes, leading to cell death.

C3b

A complement protein that tags microbes for phagocytosis and participates in immune complex formation.

Classical Pathway

A complement activation pathway initiated by antigen-antibody complexes, part of the adaptive immune response.

Lectin Pathway

A complement activation pathway that begins when soluble proteins recognize microbial antigens.

Alternative Pathway

A complement activation pathway that can be initiated by serum components and proteins without antibodies.

Anaphylatoxins

C3a, C4a, and C5a, which induce inflammatory responses and recruit immune cells to sites of infection.

Phagocytosis

The process by which immune cells engulf and destroy pathogens.

Cytokines

Soluble mediators released during inflammation that increase vascular permeability and recruit leukocytes.

Opsonins

Special proteins, such as antibodies and complement components, that enhance phagocytosis by marking invaders.

CD46

A regulatory protein that, when lost, triggers immune clearance.

Collectins

A family of calcium-dependent carbohydrate-binding proteins, including mannose-binding lectin (MBL).

C5 Convertase

A complex formed during complement activation that cleaves C5, leading to MAC formation.

Pattern Recognition Molecules

Proteins that identify and bind to molecular patterns on pathogens to initiate immune responses.