Week 6 + 7 Flashcards
Define immune system, immune response, and immunology
- immune system: collection of cells, tissues, and molecules that mediate resistance to foreign elements (antigens)
- immune response: coordinated reaction of these cells and molecules to antigens
- immunology: stud of the immune system, including its responses to microbial pathogens and damaged tissues, and its role in disease
Define antigen and epitope/antigenic determinant
- antigen: “antibody generator”, molecules that induce an immune response when introduced to the body
- epitope (antigenic determinant): part of an antigen that is actually responsible for inducing the immune response and binding to the products of the immune response (lymphocyte receptors + antibodies)
If the immune system is unable to discriminate between foreign elements an components of its own system, what is the result?
- autoimmunity
- immune responses should only be generated when components of the immune system come into contact with non-self elements
What are the two types of immune defense?
- innate immunity (NON-SPECIFIC): physical barriers, inflammation, complement
- adaptive immunity (SPECIFIC): humoral immunity, cellular immunity
What are features of innate and adaptive immunity?
T/F: there are not many physical or chemical aspects of the immune system
- false
What are PAMPs?
- pathogen-associated molecular patterns
- components that are shared between different types of pathogens and present a molecular composition that differs from “self”
What are DAMPs?
- damage-associated molecular patterns
- released when cells die (intracellular DAMPs) or generated when connective tissue is damaged (extracellular DAMPs)
What are pattern recognition receptors (PRRs)?
- receptors of innate immunity that recognize PAMPs and DAMPs
- soluble or membrane bound
- signalling of phagocytic
T/F: the immune system consists of just white blood cells
- false
What are some features of neutrophils?
- appearance: segmented nucleus, granular cytoplsam
- location in health: blood
- lifespan in health: 48-74 hrs
- primary function: antimicrobial effectors, primarily in acute bacteria infection
- mechanism of action: phagocytosis, degranulation, neutrophil extracellular trap formation
What are some features of eosinophils?
- appearance: characteristic eosinophilic granules
- location in health: blood no tissue lining gastrointestinal tract and airways
- lifespan in health: days to weeks
- primary function: antiparasitic effectors, particularly in helminths infection, some antiviral action, roles in allergy
- mechanism of action: degranulation, limited phagocytosis
What are some features of basophils?
- appearance: characteristic blue-purple basophilic granules
- location in health: blood
- lifespan in health: days
- primary function: mediator of inflammation
- mechanism of action: degranulation
What are some features of mast cells?
- appearance: round nucleus, cytoplasm densely packed with purple granules
- location in health: tissue,particularly connective tissue surrounding vasculature +nerves,and lamina propria of the mucosa
- lifespan in health: weeks to months
- primary function: immune surveillance, mediator and amplifier of inflammation and allergy
- mechanism of action: detection of threats ad release of inflammatory mediators via degranulation (vasoactive amines) or synthesis of lipid mediators and cytokines
What are some features of macrophages?
- appearance: round nucleus, clear-vacuolated cytoplasm, irregular cell shape
- location in health: peripheral tissue
- lifespan in health: months
- primary function: immune surveillance, moderate antimicrobial capacity, limited antigen presentation
- mechanism of action: detection of threats and release of inflammatory mediators, phagocytosis
What are some features of dendritic cells?
- appearance: round nucleus, clear cytoplasm, irregular shape w/ long branched projections (dendrites)
- location in health: tissues
- lifespan in health: months
- primary function: immune surveillance, antigen processing and presentation
- mechanism of action:detection of threats and release of inflammatory mediators, endocytosis and phagocytosis
What are some features of natural killer (NK) cells?
- appearance: large lymphoid cell, round nucleus, azurophilic cytoplasmic granules
- location in health: blood, spleen
- lifespan in health: months
- primary function: destruction of virally infected or abnormal host cells (including tumor cells)
- mechanism of action: recognition of virally infected or abnormal host cells and targeted release of cytotoxic granules
What are some features of lymphocytes?
- appearance: round nucleus, clear cytoplasm, high N:C ratio
- location in health: blood, tissues, secondary lymphoid organs
- lifespan in health: weeks to months, years (memory cells)
The two major types of lymphocytes are:
- T cells + B cells
What are some differences between T cells and B cells?
What is the complement system?
- collection of plasma proteins that are individually inert but can interact in a cascade once they are activated
- attacks the cellular membrane leading to cell death
-act as signalling molecules that. Recruit immune cells to inflammatory sites
What molecules communicate via cell-to-cell contact in the immune system?
- receptors: expressed on the surface of a cell Orin intracellular compartments
- ligands: molecules that activate receptors, soluble or membrane bound
What are cytokines? Some features?
- proteins with diverse functions such as cell growth, activation
- interleukins: communication between cells
- chemokines chemotaxis
What are the sentinel cells of the immune system?
What activates sentinel cells? What does this cause?
- exposed to PAMPs, DAMPs, or pro-inflammatory cytokines
- cell activation
- upregulation of cellular antimicrobial defenses
- release of pro-inflammatory chemokines, lipid mediators, an cytokines
What role do mast cells play in inflammation?
- vasocative molecules
- histamine
- serotonine
- vasodilation
- raise vascular permeability
- more leukocytes
- easier to migrate to tissue
What are systemic consequences of inflammation?
Describe leukocyte extravasation
- macrophages and dendritic cells produce cytokines such as that activate the endothelial cells to express selections and ligands for integrins and to secrete chemokines
- selectins: rolling
- integrins: adhesion
- chemokines: migration
What is leukocyte chemotaxis?
Describe leukocyte kinetics during inflammation
- lymphocytes are present once the adaptive immune system is engaged in the response
- monocytes/macrophages predominate at later stages of inflammation
- neutrophils predominate acute inflammation
What is phagocytosis?
- an active process of capturing and ingesting foreign objects/microorganisms by phagocytes
- neutrophils and macrophages
- destruction of microorganisms, damaged cells and cellular debris, foreign objects
- induction of cytokine production
- processing and presentation of antigens
What are functions of phagocytosis?
- recognition of microbe
- endocytosis
- phagosome maturation
- fusion of phagosome and lysosome
- killing of bacteria inside the phagolysosome
What are intracellular killing mechanisms? Some features?
- oxidative pathway
- use of oxygen and glucose increases several fold “respiratory burst”
- reactive oxygen species (ROS)
- reactive nitrogen species (RNS)
- toxic to microorganisms
- non-oxidative pathway
- dependent on the action of the toxic substances present in lysosomes
- cationic proteins: damage bacterial cell wall
- lysozyme: damages the mucopeptides in the bacterial cell wall
- lactoferrin: sequestration iron inhibiting bacterial growth
- proteolytic + hydrologic enzymes: digest killed bacteria
What is the purpose of Neutrophil Extracellular Traps (NETs)?
- raise inflammatory stimulus
- extrude strands of nuclear DNA and associated proteins into the extracellular fluid
- traps and kills microbes
What is the function of Neutrophil Extracellular Traps (NETs)?
- raise inflammatory stimulus
- extrude strands of nuclear DNA and associated proteins into the extracellular fluid trapping and killing microbes
What are features of the complement system?
- collection of circulating and membrane-associate proteins
- many movement proteins are proteolytic enzymes
- activation occurs in a sequential manner
- 3 activation pathways
- alternative
- classical
- lectin
What are the three pathways of the complement system and some features?
- alternative pathway: complement proteins are activated on microbial surfaces (because complement regulatory proteins are not present on microbes, only host cells)
- lectin pathway: activated when a carbohydrate-binding plasma protein, mannose-binding lectin protein (MBL), binds to terminal mannose receptors on the surface glycoproteins
- classical pathway: activated by antibodies that bind to microbes or other antigens
What are features of the membrane attack complex (MAC)?
- breaches the cell membrane of the microbe, allowing water to rush into the cell
- destruction by osmotic lysis
What are features of type I interferons?
- produced by virus-infected cells
- non-specific response to viral infection
- IFN-alpha + IFN-beta
- inhibit viral replication
- induce a antiviral state
What is the function of natural killer cells?
- recognize and respond to infected and stressed cells
- killing of cells
- secretion of IFN-gamma (stimulates and activates macrophages)
How do natural killer cells perform their function?
What are molecules tasked with antigen processing and presentation?
- Major histocompatibility complex (MHC) molecules
- class I + II
- T cells only recognize antigens presented on a MHC molecule
What does MHC I present antigens to?
- CD8+ T cells
What does MHC II present antigens to?
- CD4+ T-cells
What activates a naive T-cell?
- dendritic cell
How do dendritic cells activate naive t-cells?
- immature DC’s encounter antigens in tissues
- migration to lymphoid tissue and maturation
- antigen presentation by mature DC’s in lymph nodes
What are the different types of activated T-cells?
- t-cell subsets
- CD4+
- Th1, Th2, Th17
- express surface molecules and secrete cytokines that activate other cells
- CD8+
- cytotoxic T lymphocytes (CTLs)
- killing of infected cells
- CD4+
What is the cellular response of CD4+ TH1 cells?
- cytokine secretion
- activation of macrophages
- activation of CTLs (CD8+)
What is the cellular response of CD8+ CTLs?
- induces apoptosis of infected cells
T/F; antigen recognition of B cells is restricted by MHC presentation
- false; not restricted
What are the kinds of humoral responses of B cells?
- activated by Th cells
- T-independent activation
What are the classes/isotypes of immunoglobulins (antibodies)?
- IgG
- IgM
- IgA
- IgE
- IgD
What are differences in Ig isotypes?
What are functions of different Ig isotypes?
What is the distribution of different Ig isotypes?
- IgM: blood
- IgG: blood + tissues
- IgA: mucous membranes
- IgE: epithelial tissue
T/F: IgM is the major antibody of secondary responses
- False: IgG (memory cells)
What is the general pathway of immune response?
