killing pathogens Flashcards
What cytokine does the effector T cell Th1 produce and its role
Produces IFN-y(gamma) and v good at activating macrophages to improve phagocytosis
What cytokines does the effector T cell Th2 produce and their roles
IL-4
IL-5
IL-13
Can activate eosinophils and mast cell activation
What cytokines does the effector T cell Th17 produce and its role
IL-17
IL-22
Activate and recruit neutrophils
What does signal 3 direct
Directs T cell effector function
How is signal 3 induced
Signal 3 given by cytokines and tells T cell the infection type (bacteria, virus, parasite) so which subset it can differentiate to
What happens after a T cell has differentiated
Th1/2/17 cells migrate to infection site to aid innate immune response
What are the different classes of B cells
IgM
IgA
IgG
IgE
What are characteristics of igM
Good complement fixer
Good opsonizer
First antibody made
What are characteristics of IgA
Resistant to stomach acid
Protects mucosal surfaces
Secreted in milk
What are characteristics of IgG
Ok complement fixer
Good opsonizer
Helps NK cell kill
Can cross placenta
What are characteristics of IgE
Defends against parasites
Causes anaphylactic shock
Causes allergies
How does the classical pathway function
Uses Ab (IgM/IgG) to identify pathogen
Ab has high affinity for its Ag increasing specificity and efficiency of complement activation
What are the three main effector functions of complement
1)opsonisation to enhance phagocytosis
2)stimulating inflammation by recruiting and activating immune cells
3)lysing microbes and cells
What are the by products of complement activation
C3a
C4a
C5a
How do the byproducts of complement activation act
Act locally - recruit cells to infection site and activate cells
What is the respiratory burst in phagosome killing
The enzyme phagocyte oxidase + cofactor NADPH oxidase initiate respiratory burst coverting O2 into reaction oxygen species e.g hydrogen peroxide
What can neutrophils produce that degrades bacteria
Elastase
How does a neutrophil die
Process called NETosis
How does NETosis work
Nucleus swells and burst extruding DNA which has anti-microbial molecules attached => can trap and kill bactreia, fungi and viruses
Which T helper cells enhance immunity to helminths
T helper 2 cells (Th2)
How does Th2 cells enhance immunity to helminths
IL-4 and IL-13 enhance muscle contractions and IL-4 promotes mast cell degranulation
How do memory T and B cells estalist effector functions
T cells committed to correct phenotype - Th1/T2/Th17
B cells committed to correct isotype/class - IgM, IgG, IgA, IgE
Why are immune cells targets for infection
Evading the killing mechanism makes infection easier (macrophage)
Immune cells migrate around the host - good transporters
Immune evasion makes it easier to manipulate immune pathways
What are characteristics of listeria monocytogenes
Can break out of phagosome and then lives ＋replicates in the cytosol
Uses host actin to move within and between cells
How are macrophages fully activated
Via the cytokine IFN-y(gamma).
What is mycobacterium tuberculosis good at
Evading phagocytosis
What does mycobacterium tuberculosis result in
Chronic infections w continual production of IFN-y(gamma) and macrophage activation
What do viral infections stimulate the production of
Type 1 interferons
What are the types of interferons
IFN-a(alpha)
IFN-B(beta)
What do type 1 IFNs induce
Anti-viral state in cells that protects them from being infected
What are the functions of type 1 IFNs
Inhibition of viral gene expression
Induces apoptosis
Promote T cell and NK cell activation
How does the Type 1 IFN function by inhibiting viral gene expression
Block viral transcription and translation
Viral RNA degradation
Autophagy (cells eat own organelles)
How does the Type 1 IFN function by inducing apoptosis
Misfolded viral proteins triggers unfolded protein response causing apoptosis
How does the Type 1 IFN function by promoting T cell and NK cell activation
Sequester lymphocytes in LN
Increases cytotoxicity of CTL and NK cells
Promote Th1 differentiation
What do NK (natural killer) cells target
Target cels infected with bacteria, virus and protozoa
How are perforin and granzyme used as killing mechanisms
Perforin creates a pore in the infected cells membrane
Granzyme enters via pore and induces apoptosis
How do Fas and Fas ligand mediated cell killing work
Target cells express Fas ligand
CTL (cytotoxic T lymphocyte)/NK express FAS ligand (FasL) activating fas
Fas activation signals apoptosis
