Humoral and Cellular Immunity

•Cellular immunity – Host defenses that are mediated by antigen-specific T cells and various nonspecific cells of the immune system.

•Humoral immunity – Host defenses that are mediated by antibody present in the plasma, lymph and tissue fluids.

The Complement System

Ricklin and Lambris 2007

Functions of the Complement System

•Viral neutralization

The Complement System

Components of the Complement System:

proteins and glycoproteinssynthesized mainly by liver5% of serumcirculate as zymogens

Designation of complement components:

numerals (C1-C9)letter symbols (factor D)trivial names (homologous restriction factor)

cleavage products – “a” and “b”

Complement Activation Pathways

Immunobiology (Garland Science 2005)

The Complement System

Complement Activation:

The Complement System

The Complement System

Classical Pathway requires antibody interaction:

The Complement System

•The three complement pathways converge at the membrane-attack complex (MAC).

Consequences of Complement Activation

Consequences of Complement Activation

Regulation of the Complement System

Regulation can occur at multiple steps in the complement system:Before assembly of convertase activityAfter assembly of convertaseAssembly of membrane attack complex (MAC)

Turnberg and Botto, 2003

Microbial Evasion•Some microbes can evade complement-mediated damage.

Schneider, et al 2007