Quiz 3 Flashcards
Which MHC class molecule is bound by CD4+ versus CD8+ presenting cells?
Class II is bound by CD4+
Class I bound by CD8+
Which genes are expressed in MHC class II molecules versus MHC class I?
DP, DQ, DR - class II A, B, C (has beta 2 microglobulin)- Class I
Which cells present class II MHC genes versus class I?
Profession antigen presenting cells - class II All nucleated cells - class I
What cytokine up-regulates type I MHC?
IFN-alpha, IFN-Beta
What are the two types of cells called when associated with class II versus class I to their respective T-cells>?
Class II - antigen presenting cell (CD4 helper)
Class I - target cell (CD8+ cytotoxic)
What is the endogenous pathway?
Takes antigens from cytosol, degraded in the proteosome and trasported via TAP to become class I
What is the exogenous pathway?
Takes antigens from the extracellular milieu, MHC II associate with invariant chain, CLIP, presented on plasma membrane
What is the process of T cell development?
Hematopoiesis -> pro T cell (thymus) -> double neg (pre T)–> double positive (immature T cell) –> Single positive stage (mature Th/Tc cell) –> Naive T cell enters circulation
What are the two signals that t cells need for activation?
TCR engagement (TCR:antigen+Self-MHC and a costimulatory signal (CD28:B7 APC) -those only getting one signal is anergized
What does IL-2R bind and do?
IL-2R is a trimeric receptor needed for IL-2 binding and signaling at cytokine levels (T cell proliferation)
alpha - low affinity
beta/gamma -0 intermediate affinity
alpha/beta/gamma - high affinity
What is the difference between effector and naive t cell rolling?
Naive T cell rolling/diadepsis by sialy-Lewis (l-selectin), effector T cells through E/P-selectin
How is the t cell immune response down regulated?
Stop synthesis of IL-2/IL-2R and increased expression of TGF-Beta
What does Th1 secrete?
Makes IL-2, IFN-gamma, - USEFUL FOR CELL MEDIATED IMMUNITY
Induced by IL-12, IFN-gamma
What is Th1 particularly effective against?
Viruses, intracellular bacteria, malignant cells, fungi, extracellular bacteria
What does Th2 make?
IL-4, IL-5 - USEFUL FOR HUMERAL IMMUNITY
Induced by IL-4, IL-10
What is Th2 effective against?
Extracellar bacteria, helmithic parasites, extracellular viruses, allergic disease
What do Treg cells make?
TGF-beta, IL-10 for downregulation of immune response
Induced by TGF-beta, and low IL-6, IL-23
What does Th1 promote versus Th2?
Th1 - activates macrophages, NK cell, and increased cytotoxic activity
Th2 - b cell activation and antibody production, and isotype switching
What is the difference between memory and naive CD4 t cells?
CD45RO - memory
CD45A - naive
what are other mechanisms of CD4 t cell activation?
Mitogens - non-specifically activate T cell or B cell Superantigens - trigger TCR but are NOT processed, capable of bind directly to MHC class II to activate a significant number of T cells
What is the role of Th17 cells?
They are proinflammatory cells, induce neutrophil recruitment, produce IL-17, IL-6, induced by IL-23, IL-6, TGF-Beta, and lack of other cytokines until Th1/Th2 are upregulated
Which antigens stimulate B cells directly in absence of T cell help?
LPS, and polysaccharides with repeating identical determinants
-Produces IgM»>Ig anything else
Which helper cell aids in B-cell proliferation and how does it do it?
BCR binds antigen, Th2 cells deliver 2nd signal via CD40L and cytokines
What co-stimulatory signals are required for B-cell activation?
CD28 on T cells & B7 Complex (CD80/CD86) on Bcells
CD40L on T cells and CD40 on B cells
What is hyper-IgM syndrome?
Absence of functional CD40L
Which cytokine is responsible for switching to IgE
IL-4
Which cytokine is responsible for switching b cell to IgA
IL-10, TFG-beta
What is the role of follicular dendritic cells?
Trap antigen and lymphocytes, antigen presented on surface of FDC to b cells
Which cells play an important role in controlling viral infections?
Cytotoxic CD8+ cells that can directly kill virally infected cells and making cytokines such as IFN-gamma that inhibit vial reproduction
What is the big difference between apoptosis and necrosis?
Apoptosis - suicide, cell shrinkage and plasma membrane integrity is preserved
Necrosis - murder, loss of membrane integrity and cellular swelling
What is the Ca++ dependent mechanism of killing target cells?
Release of granules from CD8+ cells including perforin, and granzymes
What is the Ca++ independent mechanism of killing target cells?
Expression on the surface of the CD8+ cell of cytokines (IFN-gamma, INF alpha and beta) that signal apoptosis such as FasL
What is the CD4+ independent mechanism in which naive CD8+ cells differentiate into effector cytotoxic CD8+ cells?
Dendritic antigent presenting cells through MHC class I/antigen complex and costimulated through CD28 receptor
What is the CD4+ dependent mechanism in which naive CD8+ cells differentiate into effector cytotoxic CD8+ cells?
CD4+ upregulate B7-1 and produce IL-2
What are the requirements for effector CD8+ cytotoxcity?
Adhesion between effector and target cells (LFA-1 w ICAM-I) or CD2 w LFA3, and TCR activation by MHC class I/Ag
What are the effector functions of NK cells?
Cytotoxicity (mediated by perforin/granzymes and FasL) Cytokine production (IFN gamma, TNF alpha, IL12)
What do NK cells target and how do they kill their target cells?
Viruses, killing by release of granules that contain perforin and granzymes. Also express Fas: that will kill cells with Fas receptor
How do NK cells recognize their targets?
They target cells that lack HLA class 1 expression
How do NK cells kill cells coated with antibodies?
NK cells express Fc-gamma-RIII or CD16 that binds IgG1, IgG3 and kill via antibody dependent cell mediated cytotoxicity
What are the two types of NK activator and inhibitor receptors?
C-type lectin family receptors (CD94, NKG2)
Killer cell immunoglobulin-like receptors (KIRs)
How is infection blocked from being deposited and absorbed?
Secretory IgA, mucociliary apparatus, nonspecific mucoproteins
How is infection propagated?
Virus replicates within the host cell, leading to cell death via apoptosis, infections viral particles are released for hours after cell death
What is normal, fever, and high fever?
Normal - 98.6 F = 37 C
Fever - 100.5 F = 38 C
High fever - 104 F = 40 C
What exogenous and endogenous factors are released during fever?
Exogenous - PAMPS, bacterial SA, LPS
Endogenous - DAMPS, IL-1TNF, IFN
Which cytokine is responsible for inhibition?
IL-10, inhibits cytokine production, inhibits inhibition of apoptosis of neutrophils
What is the immune system function?
Resist pathogens, microbes that cause diease, foreign bodies and abnormal cells. Resistance to pathogens is primary
What makes a bacteria gram positive?
Thick peptidoglycan layer
How does extracellular bacteria cause pathology?
Inflammation, or producing toxins
How does intracellular bacteria cause pathology?
Causing chronic infections which activate and sustain immune response against host tissue
What is unique about parasites?
Unicellular and multicellular eukaryotic organisms that account for more morbidity and mortality
What are the exterior defenses?
Skin, mucosal epithelium, lysozyme in secretions, acidic environment of the stomach
What are interior defenses?
Causes inflammation, neutrophils, macrophages, innate defense mechanisms are presents prior to exposure to infectious agents
What are the receptors of innate immunity?
Pattern recognition molecules, toll-like receptors
What is the general immunity for extracellular bacteria?
opsonizing antibody IgG enhances phagocytosis, C3b, neutralizing antibody, complement activation
What is the general mechanism for intracellular bacteria?
CD4+ T cell to Th1 secreting IFN-gamma to activate macrophages, CD8+ T cell into cytotoxic T cells
What is the evasion strategies for bacteria?
Exotoxins, IgA protease, capsules, prevention of phagosome0lysosome fusion, escape from the phagosome
What is the mechanism immunity to viruses?
Inhibit IFN alpha and beta, NK cell lysis, neutralizing antibodies IgG, IgA, complement, cell mediated
What are virus evasion strategies?
Down regulation of MHC class I proteins (attacked by NK cells), Virokines (EBV) and viroreceptors (IL-10)
What is the mechanism for immunity to parasites?
Macrophages, Th1 responses are most important, activation of Th2 results in IgE, activation of eosinophils
What is the evasion strategies of parasites?
Cuticle formation, antigenic variation
