Lecture 1 part 4 Flashcards
What do bacteria need to survive/replicate?
Suitable environment
Source of nutrients
Protection from harmful elements (virulence mechanisms)
Note: Virulence mechanisms allow a pathogen to outcompete host cells and resist their defense
What are the factors affecting infection?
Type of agent
Virulence of agent
Means of exposure
Dose of the agent
Susceptibility of host to agent
List some of the innate defense mechanisms.
Barriers to infection
Phagocytic cells
Complement
Native defense cytokines
Natural killer (NK) cells
List some of the adaptive defense mechanisms.
Humoral=antibodies
Cell-mediated immunity: T-helper cells (cytokines), Cytotoxic T-cells, Gamma-Delta T-cells
Describe the process of acute inflammation.
- ) Tissue damage causes release of vasoactive and chemotactic factors that trigger a local increase in blood flow and capillary permeability.
- ) Permeable capillaries allow an influx of fluid (exudate) and cells.
- ) Phagocytes migrate to site of inflammation via chemotaxis.
- ) Phagocytes and antibacterial exudate destroy bacteria.
What are the major innate and adaptive defense mechanisms against extracellular pathogens?
Innate: Complement activation, Phagocytosis by phagocytes, Extracellular killing
Adaptive: B-cells and Helper T-cells, Antibodies (humoral)
What are the major innate and adaptive defense mechanisms against intracellular pathogens?
Innate: NK cytotoxicity
Adaptive: Cytotoxic T-cells (cell mediated), Macrophage and Helper T-cell (cell mediated)
List the anatomical and physiological barriers of the innate immune system.
skin
mucus
normal gut flora
stomach acid
antimicrobial peptides (defensins)
List some of the benefits of having microflora in the gut.
Excludes harmful pathogens
Important in the proper development of lympoid organs
Regulate B and T cell function
Note: if you lose normal gut flora you increase the likelihood of infection.
What immunoglobulin is found in mucus?
IgA
Name the two examples given in class of when barriers are disrupted.
Keratoconjunctivitis sicca (dry eye)
Foot rot
Give a list of the cells that participate in innate immune defense.
What are sentinal cells able to detect?
Phagocytic cells: Neutrophiles and Macrophages
Sentinal cells: Dendritic cells, Macrophages and Mast cells
Sentinal cells are able to detect PAMPs.
List some of the antibacterial actions of neutrophils.
- ) Lysozyme (bactericidal)
- ) Defensins (bactericidal)
- ) Lactoferrin (binds iron)
- ) Collagenase (degrades bacteria and tissue)
- ) Gelatinase (degrades bacteria and tissue)
- ) Myeloperoxidase (Respiratory burst)
Name the 3 pathways of complement activation
Classical pathway
Lectin pathway
Alternative pathway
What is the end product common to all 3 complement pathways?
Membrane attack complex (MAC).
True or False: IgM is more efficient at initiating the classical pathway than IgG.
TRUE.
Because IgM is a pentamer, it does not require multiple antibodies to activate C1.
Which complement protein is highest in concentration in the blood?
C3.
What is the function of the membrane attack complex (MAC)?
Creates a pore in a cellular membrane, leading to cellular lysis.
Which complement activation pathway is reliant on the adaptive immune system?
Classical pathway
Requires antibodies for C1 binding.
True or False: The lectin and alternative pathways can be activated without the presence of antibodies.
TRUE
These pathways are considered as part of innate immunity.
Which complement molecule is responsible for opsonization of pathogens for later recognition by phagocytic cells?
C3b
Describe the process occuring here.
Two IgG molecules are bound to a membrane. C1 has cross-linked the two IgGs, causing a conformational change in C1 to expose its active site.
C5 convertase cleaves C5 into C5a and C5b. What are the major functions of C5a?
Phagocyte chemotaxis
Mast cell degranulation
Neutrophil activation
What is the function of mannose-binding lectin (MBL)?
Binds to mannose molecules present on pathogen surfaces.
Functionally similary to C1. Initiates the lectin pathway of complement activation.
