Complement System and Innate Immunity

These flashcards cover key concepts and vocabulary related to the complement system and its role in innate immunity.

Complement System

A group of serum and cell surface proteins activated by factors such as the combination of antigen and antibody, resulting in enzyme cascades with various biological consequences.

Opsonization

The process of coating the surfaces of pathogens with C3b to enhance phagocytosis.

C3 Convertase

An enzyme complex that cleaves C3 into C3a and C3b, crucial in the complement activation pathways.

Membrane Attack Complex (MAC)

A structure formed by complement proteins that punctures the outer membrane of pathogens, leading to cell lysis and death.

Classical Pathway

A complement activation pathway initiated by the binding of antibodies to antigens, requiring two IgG or one IgM for C1 binding.

Alternative Pathway

A complement activation pathway that is continuously activated through the spontaneous breakdown of C3, allowing indirect recognition of pathogens.

MB-Lectin Pathway

A complement activation pathway that does not require antibodies and is initiated by the binding of mannose-binding lectin to microbial surfaces.

C5b

A component in the terminal complement pathway that, when bound to C3b, initiates the formation of the membrane attack complex.

C5a

A potent chemoattractant released during complement activation that triggers inflammation and attracts immune cells.

PAMPs (Pathogen-Associated Molecular Patterns)

Molecular patterns recognized by the immune system that are indicative of microbial infection, triggering innate immune responses.

Complement Regulation

Mechanisms that control and limit complement activation to prevent damage to host tissues.

IgM

An antibody that is the most efficient in activating the classical pathway of the complement system due to its pentameric structure.

C4b2b

The classical pathway C3 convertase formed during complement activation, crucial for the cleavage of C3.

C3bBb

The alternative pathway C3 convertase that cleaves C3 and amplifies the complement response.

C1

The first protein in the classical complement cascade that requires the binding of two antibody Fc regions to initiate activation.

Chemoattractant

Substances that attract immune cells to sites of infection or inflammation.