Innate Immunity Flashcards
Receptor
a structure on the surface of a cell (or inside a cell) that selectively receives and binds a specific substance
Ligand
Any molecule that binds to another, in normal usage a soluble molecule, such as a hormone or neurotransmitter, that binds to a receptor
Opsonin
(opsonisation) – An antibody or product of complement activation in blood serum that causes bacteria or other foreign cells to become more susceptible to the action of phagocytes.
Phagocytosis
Endocytosis of particulate material, such as microorganisms or cell fragments
Inflammation
a response of body tissues to injury or irritation; characterized by pain, swelling, redness and heat
Innate (natural) immunity
immunity that is naturally present and is not due to prior sensitisation to an antigen from, for example, an infection or vaccination
natural barriers against antigen entry
skin, mucosal epithelium, cilia, acid pH in stomach and vagina, lysozyme in tears and other secretions, commensal bacteria in gut, skin etc., cough and sneeze
microbial antagonism
normal bacterial flora of the body supress the growth of potentially pathogenic bacteria and fungi. They have a physical advantage due to their previous occupancy, they compete for essential nutrients, and produce inhibitors, such as acid and colicins
pathogen recognition receptors (PRRs)
TLRs
NLRs
RLRs
TLRs
recognise pathogen-associates molecular patterns. Activation of these stimulates innate responses of immune cells to these threats. In vertebrates, they also stimulate activation of adaptive immune system.
Cytokines
interferons and interleukins
low molecular weight regulatory proteins secreted by wbc and others in response to stimuli. Regulate the intensity and duration of the immune responses
chemokines
family of structurally related small glycoproteins, with potent leukocyte activation and/or chemotactic activity.
complement system
series of blood and tissue fluid circulating proteins. Are inactive when circulating but become activated in response to the recognition of molecular components of microorganisms. Complement cascade – binding of one promotes the binding of the next protein the cascade
functions of complement cascade
makes bacteria more susceptible to phagocytosis (oponisation), directly lyses some bacteria and foreign cells using a membrane attack complex, produces chemotactic substances that mediate inflammation, increases vascular permeability, causes smooth muscle contraction promoting mast cell degranulation
3 types of complement cascade
Classical – activated by antigen-antibody complexes
Alternative – activated by C3b binding to microbial surfaces ad antibody molecules
Lectin – activated by lectin binding to mannose on pathogen surface
