Lecture 4 - 8/29/19 Flashcards
(24 cards)
why does alternative pathway activate first
because the C3 can bind any hydroxyl group and any amino group on a protein or other things
what type of system can classic pathway work in
both innate and adaptive
what are defensins
penetrate pathogen membrance causing its disruption. they’re secreted at mucosal surfaces. also produced by neutrophils and stored in the granules. alpha is produced by intestinal epithelial cells. beta is produced by epithelial cells in a broad range of tissues
what are pentraxins
short ones are synthesized by liver. long ones by a variety of cells. circulate in blood and lymph and target pathogens to be destroyed. Act as a bridge between pathogen and phagocyte (similar to Ab)
describe immediate innate response
0-4 hours pathogen invades tissue and proliferates. pathogen is recognied by preformed soluble effector molecules and resident effector cells in the infected tissue. pathogen is either eliminated and infection ends or pathogen is not eliminated; proceed with the induced innate immune response.
describe induced innate immune response
4 hours to 4 days. pathogen invades tissue and proliferates. activation of cells resident in the infected tissue. recruitment of effector cells to the infected tissue. inflammation, fever, the acute-phase response. soluble effector molecules and UNF
what are cytokines
they’re proteins that mediate the effector functions of the immune system. they act on specific receptors expressed on other leukocytes. most are soluble proteins; released by one cell, bind to receptors of another cell, induce biological effects. very few but some are membrane-bound (TNF family) they regulate intensity, form and duration of immune response
are cytokines ag-specific
no they’re not. only those lymphocytes responding to a specific immunogen are affected by cytokines; these lymphocytes express the correct cytokines receptors. direct cell-to-cell interactions between cells responding to the same Ag.
what factors do cytokines effects depend on
the target cell, the state of differentiation of the target cell, the presence or absence of other cytokines
name 3 cytokines effects
endocrine action - released into the bloodstream to bind distant cells. paracrine action - released to bind nearby cells. autocrine action - released, bu then bind to receptors on the cell that produced them
describe receptors on innate immune cells
each R recognizes multiple pathogenic species so a few number of receptors are needed. there are about 100 different R and each cell type expresses only a subset of them
list some phagocytic and signaling receptors on macrophages
mannose receptor, complement receptors 3 and 4, dectin-1, macrophage receptor with collagenous structure (MARCO) scavenger receptor A (SR-A) scavernger receptor B (SR-B) UNF
describe TLR4
toll-like receptor on MQ recognizes LPS on bacteria and induces change in gene expressions. activation of TLR4 leads to the activates of the transcription factor NFkB.
what all can member of TLR recognize
virus, fungi and parasites. extracellular: cell plasma Mb receptors recognize ligands on he stuface of pathogen. intracellular on endosomes recognize nucleic acid from pathogens
describe IL-1beta and TNF-alpha cyotokines
induce blood vessels to become more permeable, enabling effector cells and fluid containing soluble effecotr molecules to enter the infected tissue.
describe IL-6 cytokine
induces fat and muscle cells to metabolize, make heat and raise the temperature in the infected tissue. increases production of acute-phase proteins by the liver
describe CXCL8
recruits neutrophils from the blood and guides them to the infected tissue (chemoattractant)
describe IL-12 cytokine
recruits and activates natural killer (NK) cells that in turn secrete cytokines that strengthen the macrophages’ response to the infection
where do the previously described cytokine come from
resident macrophages secrete the cytokines
describe interferons (IFN) family of cytokines
the most important kind of cytokine during viral infections. type I interferon genes are transcribed as a result of sensing double-stranded RNA
describe proudction of IFN by virus-infected cell
IFN makes infected cell more susceptible to be attacked. binds to NK cells to activate them and are drawn to site of infection.
describe NK cells
responders during innate immunity, form synapses with infected cells and with MQ, activated by IFN type I
what are the functions of NK cells
non-phagocytic but cytotoxic: kill tumor and/or virus-infected cells. form NK-cell synapse, produce cytokines (increase state of inflammation, production of cytokines by MQ, increase MQ phagocytic activity, so an overall increase in inflamation)
what is special about NK cells
only cells that express TLR 3 and TLR8, both intracellular. main source of IFNy during innate response