Immunology 3 Flashcards
Nk cells kill target cell coated with ____ by ____?
target cell coated with IgG antibodies, via ADCC aka antibody dependent cell mediated toxicity
NK cell: what type of Fc receptor? meaning?
low affinity Fc receptor: doesn’t capture antibodies out of solution, but multiple Fc receptors bind multiple antibodies lined up on surface of target cell - since that depends on overall avidity of interaction
mast cells: what type of Fc receptor? which means?
high affinity Fc receptor specific for IgE = can capture them out of solution
what is the complement?
circulating serum proteins that are activated in a sequential proteolytic cascade - will bind together to make complexes
how can complement be activated
classical pathway = by antibody/antigen complexes lining up the Fc regions just right. alternate pathway = continuously forming spontaneous complement complexes that are degraded by complement regulatory proteins on self cells, but bacterial/pathogenic cells don’t have them = cascade of activated complexes form
2 ultimate results of complement activation
complex of complement proteins stuck onto microbial cell surface = enhance phagocytosis. membrane attack complex can insert a pore if the cell doesn’t have a thick rigid wall
complement: which is innate vs. acquired?
innate immune system = alternate pathway acquired system = classical pathway, since it requires antibodies
after MAC: fragments?
cleaved complement fragments (orange tags) = soluble proteins with inflammatory properties, will activate granulocytes + mast cells
4 things complement activation can do
cell lysis. phagocytosis (opsonization). mast cell activation, neutrophil recruitment and inflammation (via floating away tags). solubilization of immune complex
which antibodies can or can’t activate complement
antigen bound IgM and antigen bound IgG can activate, soluble IgM and IgG can’t
why can’t soluble IgG or M activate complement
soluble IgM has an inaccessible Fc (in the middle). soluble IgG has PC portions not adjacent
C1 needs to bind to what to initiate what
two or more Fc portions to initiate the complement cascade
T cell receptor structure
similar to antibodies: dimer of two chains, each chain with a variable and constant domain in the extracellular portion + hydrophobic transmembrane domain + short intracellular tail
T cell receptors are only expressed as? binding sites?
cell surface molecules. two polypeptide chains + one binding site.
TCRs expressed on cell surface only in association with?
other proteins = complex of TCR + CD3
CD4/CD8 not sufficient for? so you need?
insufficient for activation of T-cells: you need additional costimulation
costimulation (to activate T cells) mediated by?
other cell surface molecules on T cells interacting
important costimulation for CD4 helper cells
B7 and CD28
CD4: which autocrine growth factor?
IL-2
