Chapter 2 Vocab Flashcards
Innate immune responses
The “workhorse” of the immune system. It stops most infections before symptoms are noticed. Only those pathogens that escape the innate response activate the adaptive response.Typically these responses are non-specific.
Barrier defenses
The first line of defense against pathogens. Skin and mucosal tissues act as barrier defenses.
Exotoxin
a toxin released by a pathogen into its surroundings
Endotoxin
toxins found in the cell walls of certain pathogens that cause the immune system to overreact
Extracellular
outside of the cell
Intracellular
inside of the cell
Complement
Complement is a system of plasma proteins that can be activated directly by pathogens or indirectly by pathogen-bound antibody, leading to a cascade of reactions that occurs on the surface of pathogens and generates active components with various effector functions.
The complement system is composed of proteins made by the liver and released into the bloodstream, lymphatic system, and extracellular spaces. Many of the complement proteins are proteases – enzymes that catalyze the degradation of proteins. They mark pathogens in a non-specific manner. Regardless of the path of complement activation, the outcome is the fixation of C3b to the surface of the pathogen. C3b is recognized by effector cells and stimulates phagocytosis of the pathogen (i.e., C3b’s attachment does not kill the pathogen, but marks it for destruction).
Alternative complement activation pathway
the pathogen surface creates a local environment conducive to complement activation; this is the first pathway to act.
DAF, MCP, Factor I, Factor H
DAF, MCP, and Factor H, and Factor I are complement control proteins that can protect human cell surfaces.
Factor P
protects C3 convertase from degradation
Complement receptors
Receptors on the surfaces of macrophages that recognize complements coated on pathogen surfaces
Membrane attack complex
A complex of complements led by C5 (which is activated by alternative C5 convertase) that makes holes in the membranes of pathogens.
Anaphylatoxins
Inflammatory mediators like C3a and C5a that can induce systemic inflammatory response known as anaphylaxis. Anaphylatoxins induce vascular permeability, act as chemoattractants for neutrophils and macrophages, and increase expression of CR1 and CR3 on these cells.
alpha 2-macroglobulin
inhibits proteases
Defensins
Defensins are antimicrobial peptides. They are amphipathic (have hydrophilic and hydrophobic regions) and can insert themselves into the membranes of pathogens and disrupt the integrity of their membranes. They work better in the harsh environments of the gut lumen, tears, of phagosomes.
