Immunology Answers – Flashcards
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| What is the function of lactoferrin as an antimicrobial? |
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| This complexes with most available Fe; bacteria must uptake Fe to survive. |
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| What is the function of apolactoferrin as an antimicrobial? |
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| Complexes with receptors on certain cells that bacteria use to enter these cells. |
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| What opsonizers can activate the complement pathway? |
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| C-reactive protein, serum amyloid protein, mannose binding lectin, C3, antibodies |
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| Which cells secrete the plasma proteins (such as C reactive protein) that opsonize bacteria? |
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| hepatocytes. These are secreted continuously, but CRP and SAP are rapidly upscaled in the case of infection. |
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| What are the three pathways for C3 activation? |
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| classical: antibody binds to pathogen, attracts C1 (a protease) which bind+ cleaves C2 + C4, which together cleave C3 alternate: C3 binds pathogen itself, cleaving spontaneously lectin pathway: mannose-binding lectin (a serine protease) binds to pathogen, recruits and cleaves C2/C4 |
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| What is the positive feedback loop in C3->C3b conversion? |
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| C3b is a component in an alternate form of C3 convertase (C3b+Bb) |
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| What are the components of C5 convertase? |
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| C3b + C3 convertase (either C3/Bb or C2/C4 form) |
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| What is the effect of C5a/b? |
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| C5a is a chemoattractant for phagocytes. C5b attracts other complements to form a lysing device (membrane attack complex). |
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| Which complement turns on the adaptive immune system? |
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| C3d |
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| What are the primary activites of NK cells in response to viral attack? |
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| 1. use granules to promote apoptosis of infected cells 2. release INF-gamma to recruit macrophages |
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| What part of the immune system does INF-a,b turn on? |
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| Systemic effects - all cells that encounter enter anti-viral state (increased proteolysis, viral mRNA degradation) Also, NK's are turned on. |
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| What larger class of receptors is a toll-like receptor a member of? |
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| PAMP (pathogen associated molecular pattern) receptors |
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| Which cytokines are fantastic at activating macrophages? Who secretes them? |
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| IFN-y ("gamma"), secreted by NK cells (among others) |
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| What are the effects of mast cell granules? |
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| Redness (increased capillary engorement) swelling ("", + increased leakiness due to tight junction breakdown) Pain - stimulation of nociceptors Both effects mediated by serotonin and histamine |
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| What are the effects of mast cell granules? |
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Histamine, serotin, heparine: pain, redness, swelling (neutrophil chemokine), clot-freeness (short-term) prostaglandins, leukotrienes Neutral proteases: cleaves C3->3a, tissue damage to promote clots and scars Prostaglandins and leukotrienes -> swelling and bronchospasm IL-4 and TNF -> attract neutrophils and eosinophils, systemic inflammation
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| what are the primary cytokines that mast cells secrete? |
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| IL-4 (attracts especially eosinophils), TNF-a |
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| What are the 4 functions of macrophages? |
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| 1. phagocytose 2. Antigen presentation 3. cytokine secretion (can modify adaptive immune system, recruit NK's, cause inflammation among others) 4. healing - by stimulating angiogenesis + fibrosis |
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| What are the affects of TNF? |
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| activate neutrophils and endothelial cells (inflammation, stickiness), cause hypothalamic fever, cause hepatic acute phase protein production, cause muscle/fat catabolism, enhance apoptosis. |
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| What is in neutrophil specific and azurophilic granules? |
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| azurophilic - myeloperoxidase (makes bleach) specific - lactoferrin, lysozyme |
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| How do antibodies activate mast cells/eosinophils? |
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| IgE is already on the mast cell/eosionphil membrane - binding of antigen activates the cell. |
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| What are the actions of major basic protein? Who secrets it? |
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| 1 a) mast cell degranulation b) proteolysis of sulfated proteoglycans (heparin, parasites) 2 eosinophils |
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| What is the nature of eosinophil granules that makes them well-suited to fighting parasites? |
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| they secrete several enzymes that break down tough outer coverings of parasites, including MBP, acid phosphatase, elastase |
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| Which T cells express CD4/CD8? |
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| Helper T cells - CD4. Cytotoxic T cells - CD8 |
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| Which cells express MHC II? |
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| dendritic cells, macrophages, B cells (!) |
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| What type of cells perform cross presentation? |
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| dendritic cells (this is when the peptides leak out of the phagosome to present to cytotoxic T cells via MHC I) |
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| What protein moves antigenic peptides from the cytosol to the ER? |
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| TAP - transporter associated with antigen processing |
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| What sort of lymphocytes/lymphatic tissue are found in the skin? |
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| scattered memory B's and T's, gamma-delta T's |
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| What is the name of the epitope-specific portions of variable regions in antibodies? |
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| CDR's - complementary determining regions |
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| Which Ig's are most long-lived? WhyWhich Ig's are most prevalent? Where? |
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| IgG is long lived because when it is endocytosed, the FcRn receptor makes it be recycled instead of lysosome-degraded. IgA is the most plentiful, found especially in secretions. |
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| What enzyme creates junctional diversity in antibodies and TCR's? |
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| TdT - terminal deoxynucleotide transferase |
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| Which are equivalent between heavy and light antibody chains and a and b TCR chains? |
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| heavy -> b light -> a |
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| a cell express only the heavy chain of an immunoglobin. What type of cell is it? |
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| A pre-b cell |
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| A cell expresses only IgM. What type of cell is it |
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| an immature b-cell |
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| Which type(s) of B cell can be found in the spleen that is NOT yet mature? |
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| immature B cells |
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| What stage of T cell is double-positive for CD4/8? |
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| immature T cells - pro and pre are in analgous receptor making modes to pro and pre B cells |
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| What sort of cell presents antigens to thymocytes during their education? |
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| epithelioreticular (thymic reticular) cells |
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| What is the signal and receptor (give CD #) that causes T cell proliferation? |
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| Signal is IL-2; receptor is IL-2 a,b,y subunits. a-subunit is CD 25 |
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| When APC's bind to T cells in a synapse, what is the primary means of causing differentiation of the T cell? |
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| cytokines (not membrane-bound receptors/ligands) |
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| what is the effect of INF-a? |
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| this is a type I interferon (like INF-B), so it turns cells into the "antiviral" state |
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| What do HLA genes encode? |
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| MHC molecules |
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| what is invarient chain? What are steps of its removal? |
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| it's a protein that binds MHC II to stabilize it/ prevent it from binding ER proteins. Degraded into CLIP, then removed by HLA-DP |
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| What do all T cells display (CD)? |
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| CD3 |
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| What is NF-kB? |
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| a pro-inflammatory transcription factor |
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| What determines what sort of Th into which the mature-naive T cell will differentiate? |
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| cytokines from APC - reflects which PAMP (TLR) receptors were activated and what the cytokine milieu around the infection was and what the genetics of the host are. |
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| Why do activated Th cells still need TCRs? |
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| They should only secrete cytokines at the point of infection |
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| What is the overall function of a Th2 cell? |
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| 1) stimulate eosinophil/mast cell inflammation 2) stop classic macrophage-driven inflammation 3) promote Th2 formation and diminish Th1 formation |
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| What are the different effects of Th2 vs. Th1 cells on innate immunity and B cells? |
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| Th2 - M2 (repair/fibrotic) macrophages, eosinophils/mast cells active, neutralizing IgG Th1 - M1 macrophages, neutrophils, opsonizing IgG |
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| What do Th17 cells secrete? |
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| IL-17, which attracts neutrophils in the skin, mucosal areas. |
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| Name some anti-inflammatory cytokines |
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| IL-10, TGF-B |
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| What is Fas and what binds it? |
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| This is a death receptor on stressed cells; Fas ligand binds this (on cytotoxic T cell) |
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| What are granzymesPerforins? |
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| Perforins puts holes in cell endosome that has endocytosed T cell granule contents granzymes activate caspases (start apoptotic mechanism) |
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| How do CTL's help macrophages kill cells? |
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| They secrete INF-y, which makes Mq's more active, so they eat more infected cells! |
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| Are effector T cells short- or long-lived? |
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| short - they have Fas and other receptors that shut them down pretty soon after they're activated |
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| Why do NK cells kill cells which have MHC-suppressing viruses? |
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| The NK cells need a continuous negative signal (activates phosphatases which act on ITAM regions of activating receptors) to keep from killing. This negative signal is MHC+self peptide |
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| What's the signal for B-cell inactivation? |
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| a B-cell has its membrane-bound Ab bound by antigen, and has its FcyR bound by antigen-bound Ab. A "small immune complex" |
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| What is the poly-Ig receptor? |
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| Binds to J-chain of IgA/M Ab to transcytose it to gut lumen |
