L3 Cell of Innate Immunity Pt. 2 Flashcards
(33 cards)
what does eosinophils role in innate immunity require?
IgE from adaptive immunity
on Eosinophils, what does the Fc3R bind to?
IgE antibodies which bind to the epitopes on helminths
In eosinophils, the binding of IgE to Fc3R receptor causes what?
degranulation of eosinophils = release of major basic protein (MBP) and eosinophil cationic protein (ECP)
what are very toxic to helminths and other parasites?
MBP and ECP
why do eosinophils play a major role in immunity to helminths?
because they are relatively resistant to destruction by neutrophils and macrophages.
what is the role of NK cells in an immune response?
kill infected cells (viral infections)
kill some tumors
secrete cytokines that play a role in differentiation of Th0 cells to Th1
at what stage of the immune response do phagocytes destroy viruses?
after the viral infections are sequestered within the host cell and they bud and infect other cells
at what stage of the immune response do NK cells destroy viruses?
eliminate viral infections of host cells that harbor the virus before significant viral replication occurs
what are NK inhibitory and activating receptors?
- interact with specific self-Class I MHC, MHC class I-like molecules and molecules unrelated to MHC
- each receptor is linked to different signaling cascades
how are Class I MHC upregulated on target cells?
following exposure to either cytokines IFNy or IFN alpha/beta
what happens when NK inhibitory interaction is strong?
cell expressing Class I MHC is protected - cell tolerance is maintained
explain “Missing self hypothesis”
the cell displaying high levels of specific self MHC self peptide is not killed because the interaction of the NK inhibitory receptor with specific self Class I-MHC peptide delivers an inhibitory signal = tolerance!
what happens to the target cell when activating receptor signals dominant?
the cell will be destroyed (lysis)
which cytokines enhance expression of Class I MHC on a cell that is potentially a target cell?
IFNy and IFN alpha/beta
describe 3 scenarios that lead to the down regulation of Class I MHC on cells?
- stress
- some viral infections
- some tumors
what is the role of IgG antibodies in a viral infection?
- IgG antibodies bind to the virally infected cell
- IgG antibodies have an Fcy region
- the NK cell has a FcyR (receptor) that binds to it
*participates in ADCC (antibody dependent cell mediate cytotoxicity) = indirect recognition
what is antibody dependent cell mediated cytotoxicity (ADCC)?
different antibodies recognize different viral proteins embedded in the cell membrane of an infected cell and then KILL the infected cell
what is the armamentarium released by the NK cell when the activating signal dominates?
NK cells release lytic granules = perforin and granzymes –> cell destruction!
which cytokines pairs activate NK cells to secrete IFNy?
IL-12 and a second cytokine = IL-15 or IL-18
What is the role of IL-2 on NK cell formation?
activation with IL-2 enhances the ability of NK cells to kill
what is a LAK cells?
IL-2 modified NK cells = lymphokine activated killer cells
what is the consequences of IL-12/IL-18 or IL-12/IL-15 on the action of NK cells?
stimulates NK cells to secrete IFNy - plays a role in the induction of Th1 cells from Th0 cells
also leads to IFNy secretion - but not as much as IL-12/IL-18
what cells secrete IL-18?
monocytes, macrophages, dendritic cells + several non immune cells
what cells secrete IL-15
nonlymphoid tissues - epithalial, fibroblast cell lines
activated monocytes/macrophages
dendritic cells
