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61 Cards in this Set
- Front
- Back
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What cells are responsible for mediating the adaptive immunity?
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B and T cells are responsible for mediating adaptive immunity.
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What types of cells constitute the innate immune system?
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The innate immune system is comprised of Natural Killer (NK) cells, phagocytes (e.g., neutrophils and macrophages), and complement proteins.
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What type of pathogens is the innate immune system prepared to handle?
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LPS (gram negative bacteria), peptidoglycan (gram positive bacteria), and ds RNA (viruses)
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How do T cells and B cells differ in how they recognize antigens?
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T cells require linear protein antigens in the context of self major histocompatibility complex (MHC) expressed on the surface of antigen presenting cells (APCs), whereas B cells can recognize virtually any chemical structure
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What are some differences between humoral immunity and cell-mediated immunity?
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Humoral immunity is mediated by B cells and is directed against extracellular pathogens (e.g., bacteria and parasites), whereas cell-mediated immunity is mediated by T cells and is against intracellular pathogens (e.g., certain bacteria and viruses).
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What are some examples of secondary lymphoid organs?
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Lymph nodes, mucosal tissue, cutaneous surfaces, the spleen are all examples of secondary lymphoid organs, where immune responses are generated (naïve T and B cells initially encounter antigen).
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How would the degree of infection change for a person who lost adaptive immunity versus innate immunity?
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The degree of infection increases almost infinitely for one with no innate immunity, while if there is no adaptive immunity, there will be a delay after infection before the degree of infection rises significantly.
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How long are the amino acids that T-cells usually recognize?
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They are 8-20 amino acids long and linear.
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Where do B and T cells gain their full maturation (lose their naivite)?
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In secondary lymphoid organs, B and T cells encounter antigens and gain their ability to respond to antigens.
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In secondary lymphoid organs, B and T cells encounter antigens and gain their ability to respond to antigens.
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Naïve cells have no effector functions.
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What’s the life span of effector cells?
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The life span of effector cells is short (usually days)
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What do swollen lymph nodes represent?
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Palpable lymph nodes indicate an ongoing T and B cell proliferative response.
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What’s a name for the zone that B cells hang out in in lymph nodes?
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The follicular zone, follicle, B cell zone
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What is a chemokine?
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A chemokine is a small molecule that acts to induce directed migration of cells to a specific location.
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What is somatic recombination?
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During the process of development, the genes that encode the B and T cell receptors start re-arranging (somatic recombination)
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What are the steps for leukocyte migration to infectious site?
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1. Microbe stimulates innate cells to produce cytokines
2. Cytokines act on endothelial cells (form walls of blood vessels) to express selectins (carbohydrate binding molecules) 3. Circulating PMNs or monocytes express selectin ligands that bind weakly to endothelium and roll along inside of vessel 4. These same cytokines act to induce a) integrin ligands and b) chemokines which increase the ability of integrins on phagocytes to bind tightly to endothelium 5. Migration through the endothelium ensues |
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What are NK cells specialized to handle?
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NK cells are innate cells with receptors to recognize and kill virally-infected cells.
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What is C3b’s role in the complement cascade?
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C3b binds to the microbe and opsonizes it for phagocytosis.
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What 4 signs indicate inflammation?
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1) Rubor-redness
2) Calor - heat 3) Dolar – pain 4) Tumor – swelling |
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What is diapedesis?
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Migration of neutrophils and macrophages from the blood stream to areas of infection to effect immunoresponses.
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What is the complement system?
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The complement system is composed of proteolytic enzymes and regulatory proteins that are capable of causing the direct lysis of cells, like bacteria or fungi.
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What are toll-like receptors (TLRs)?
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Toll-like receptors are receptors on resident tissue cells (mast cells, dendritic cells, macrophages, NK cells) that express receptors on their surface and internally engage molecules present on mcirobes, such as bacteria or viruses (pathogen associated molecular pattern molecules – PAMP).
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Which molecule induces the differentiation of the Th1 helper T cell subset?
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IL-12 is a potent inducer of the differentiation of the Th1 helper T cell subset and also enhances the cytolytic activity of CTL and NK cells.
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MHC molecules are expressed differently depending upon the kind of cell. Which cells express MHC I?
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All nucleated cells express MHC class I molecules
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MHC molecules are expressed differently depending upon the kind of cell. Which cells express MHC II?
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Dendritic cells, macrophages, and B cells, APCs express MHC II
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Which MHCs express intracellularly-derived antigens versus extracellularly-derived antigens?
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MHC II – extracellular, MHC I – intracellular
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What are the best APCs?
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Dendritic cells, activated macrophages, and activated B cells are the best APCs
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How is antigenic diversity generated for TcR and BcRs?
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Combinatorial association of individual V, D and J gene segments and the pairing of two different Ag receptor chains to form a complete BcR or TcR is responsible for some diversity. Also: imprecise joining of the V, D, and/or J region segments adds or deletes nucleotides at the junctions, and an enzyme called terminal deoxynucleotidyl transferase is able to introduce additional nucleotide sequences at the junctions between gene segments in N region diversification.
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What are the different phases of the T lymphocyte immune response?
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Recognition, activation, effector phase, and homeostasis
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Recognition, activation, effector phase, and homeostasis
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ITAMs are immunoreceptor tyrosine based activation motifs, and they lie in the cytoplasmic domain of CD3 chains and play a critical role in the initiation of signal transduction in response to receptor activation.
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How long do the T cell and APC have to interact for T cell activation?
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4-6 hours
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Why are co-stimulatory molecules important?
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Engagement of only the Ag receptor is insufficient, and in some cases, will actually lead to a state of unresponsiveness, termed anergy.
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What’s a way to stop the immune response initiated by co-stimulatory action of CD28 with B7-1,2?
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CTLA-4, which is homologous to CD28, can get upregulated and will displace CD28, stopping the immune response. This is a way to stop the immune response.
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What is one of the roles of IL-2?
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IL-2 is an important autocrine signaling molecule secreted by activated T cells that helps with proliferation and expansion of T cells.
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What cytokine do Th1 cells produce, and what is its function?
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Th1 cells produce IFN-gamma, which is important for host defense against intracellular microbes and is a potent inflammatory cytokine.
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What cytokine do Th2 cells produce, and what is its function?
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Th2 cells produce IL-4, 5, 13, which is good for host defense against helminths (IL-4,5 also drive B cells to make IgE, which is important for defense against helminths) and good for allergic reactions.
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What cytokine do Th17 cells produce, and what is its function?
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Produces IL-17, which is good for host defense against some bacteria and fungi and inflammatory disorders.
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What cytokine is overproduced in allergic responses and important for allergic responses?
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IL-4 is overproduced in allergic responses and important for allergic responses
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Which immune cells are the most proliferative in terms of producing cytokines?
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T helper cells
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What is the mechanism for the increase in NFAT?
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CD4/CD8 binds to respective receptor, signals Lck to phosphorylate zeta, which activates Zap70, which phosphorylates adapter proteins, which activates PLCgamma-1, which increases Ca++, which activates Calcineurin which then activates NFAT.
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What is IL-2’s role for T-cells?
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Interleukin-2 is very important. It’s made by the T cell when activated, and it acts in an autocrine fashion and is critical for good proliferation and expansion of T cells.
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What are the two forms that cell-mediated immunity takes?
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1) Activation of macrophages by IFN-g secreted Th1 cells
2) Lysis of infected cells by CD8+ CTL |
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What mediates immediate type hypersensitivity?
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Immediate type hypersensitivity is IgE mediated.
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What are the 2 mechanisms by which CTLs kill target cells?
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1) Perforin-mediated cell lysis
2) FasL mediated cell lysis |
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What signaling is important for survival and generation of memory cells from Ag-activated lymphocytes?
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CD40
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What does the membrane attack complex do?
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MAC creates pores in microbial cell membranes.
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Which Abs are the first Abs made during the humoral response?
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IgM
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What is the major isotype that can activate complement?
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IgM
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Lack of what molecules predisposes individuals to autoimmune lymphoproliferative syndrome (ALPS)?
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Loss or dysfunction of either Fas or FasL results in ALPS with symptoms very similar to that of systemic lupus.
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What is the most important mechanism for turning off an immune response?
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Elimination of the Ag causes the responding lymphocytes to apoptosis, returning the system to homeostasis. (a small fraction survive to become memory cells)
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What immune response is required for the phagocytosis and killing of encapsulated extracellular bacteria by neutrophils?
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Humoral immunity with the production of opsonizing antibodies is required for the phagocytosis and killing of encapsulated extracellular bacteria by neutrophils.
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What is the most common cause of septic shock?
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Gram negative bacteria
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How does chronic inflammation injure tissue?
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Chronic inflammation injures tissue by proteases and oxygen radicals released from neutrophils and macrophages.
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What causes the formation of exudate in the interstitial spaces of acutely inflamed tissue?
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Decreased intravascular osmotic pressure (due to escape of proteins like albumin into interstitium—caused by increased permeability of blood vessel walls) is the major factor, and the minor factor is increased intravascular hydrostatic pressure. Both of these contribute to the formation of exudate.
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What is the action of IFN-gamma?
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IFN-gamma activates macrophages
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What are the two reactions that take place inside neutrophils to destroy extracellular bacteria?
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1. Myeloperoxidase reaction
a. Produces HOCl* b. Primary mechanism that kills extracellular bacteria within phagolysosomes of neutrophils 2. Fenton reaction a. Produces OH* from peroxide |
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How do granzymes help in the process of killing intracellular bacteria?
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Granzymes activate caspases in infected cells, inducing apoptosis.
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What is the mechanism and purpose of fever?
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Fever is caused by prostaglandin synthesis in the anterior hypothalamus, and it enhances the immune response.
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What are the key players in acute inflammation versus chronic inflammation?
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• Acute inflammation
o PMNs o Platelets o Mast cells • Chronic inflammation o Macrophages o Lymphocytes o Plasma cells |
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What are actions of histamine, and which cells carry histamine?
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Histamin is carried by Mast cells, Basophils, and platelets, and it stimulates endothelial cell contraction in post-capillary venules by interaction with H1 receptors, which causes increased vascular permeability and plasma exudation.
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What mechanisms/molecules are produced by the body in sepsis?
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• Cytokines
o TNF & IL-1, 6 • Coagulation cascade • Thrombotic emboli |
