Infection & Immunity Flashcards
How are microbes recognized (what do they have and what do they bind to)
PAMPS that bind to pattern recognition receptors (PRRs) that are found withing and on cell surfaces
What does the ligation of TLRs lead to
Ligation leads to production of immflamatory mediators such as cytokines, proliferation, activation and survival
What do cell surface vs endosomal TLRs primarily recognize
Cell surface= PAMPS found on the surface of microbes (bac, viruses, etc)
Endosomal- genomes of microbes that enter via endocytosis
What are the endosomal TLRs
3,7,8,9
What do TLR1/2, 3, 4 5, 7/8, 9 recognize
1/2- petidoglycan, Zymosan 3- dsRNA 4- LPS 5- Flagellin 7/8- ssRNA 9- Unmethylated CpG DNA
Where are NOD like receptors found, what do they bind and what do they do
Cytosolic PRRs
-bind peptidoglycan and other bacteria products
-Immflamatory PRRs (cytokine prod)
Where are RIG-I-like receptors found an dwhat do they regognize
Cytosolic inflammaory PRR involved in recognition of RNA virus by innate immune system
What is the complement pathway typically used against
Can be used against all classes of extracellular microbes- especially bacteria
What are the 3 functins of the complement pathway
- MAC complex- pores in microbial membrane
- Inflamation/chemotaxis- anaphylatoxins (C3a, C5a) recruiting and activating neutrophils/monocytes
- Opsonization- C3b tags microbial surfaces making microbe easier to be found by phago
What occurs in the classical, lectin and alternative pathway
classical- C1q binds antigens or antibodies IgM, IgG
Lectin- Lectins binds to microbial mannose residues on microbes
Alternative- Spontaneous activation of C3 on microbe surface
What does lysozyme do and where is it found and what is it effective against
in extracellular secretions
-hydrolyzes peptidoglycan and thus effective against gram pos bacteria (breaks down wall)
What are defensins produced by, what do they act on and what do they do
- produced by epithelial cells
- insert themselvees into the outer leaflets of bac cell membranes (causing breakage of membrane)
What are the cells that can do phagocytosis (4)
Macrophages, neutrophils, monocytes, DCs
What are the 2 phagocytic receptors and ligands
Complement recptor- C3b
FcyR- Fc region of IgG antibodies on microbe surface
What are the first responders to inf, what are they effective against and what do they do
Neutrophils
-Bact and fungi targeted by neutrophils
-perform phago and secretes extracellular traps (NETs)
What do antibodies primarily target
extracellular antigens
How are antibodies activated
TCr binds MHC II + ag on B cell
CD40 (b cell) binds to CD40L (Th1/2)
Cytokines (signal 3)
What do you need for isotype switching to mucosal IgA
Retinoic acid
What 2 antibodies perform neutralization
IgG
IgA
What occurs in neutralization
Antibody blocks binding to virus receptor or even fusion event
What does sIgA do
Neutralizes pathogens on mucosal surfaces
What antibody performs opsonization and how does it occur
IgG antibody binds to bacterium and binds to fc receptors on cell surface where it will be phagod
What antibody performs Antibody dependent cell mediated cytotoxicity and how does it work
–igG
Antibody binds antigens on surface of target cell
-Fc receptors on NK cells recognize bound antibody and kill target cell
What antibody targets parasites for removal and how
- -IgE
- IgE tags surface antigen and Fc region on eosinophil recognizes IgE and causes release of substances ( Cytokines, chemokine, leukotienes etc)
What does activated Th17 produce and what does it do
produces IL17
-IL17 binds to epithelial cells and causes the epithelial cells to produce chemokine that recruit innate phagocytes (neutrophils and macrophages)
How do exogenous antigens activate macrophages
Th1 recognizes its epitope loaded on a macrophages MHCII
-CD40L on Th1 binds CD40 on macrophage
and th1 produces IFNy which activates macrophage
How do th1 cells increase macrophage antimicrobial activity (3)
- accelerated lysosome to phagosome fusion
- Increased prod of toxic O/N compounds
- Upregulation of MHC 1/2
What are interferons
cytokines with broad antimicrobial activities
can be produced by virally infected cells as a natural response
What do Type 1 interferons stim
results in a series of cell signalling events culminating in the transcription of interferon stimulated genes (ISG)
What do interferon stimulated genes do
induces antiviral state
blocks entry, degrades cellular mRNAs, arrests cell translation, blocks egress
What are the 3 main functions of Type 1 interferons
InF B (with Il12) activates NK
- Increased synthesis of + Assembly of MHC molecules
- induce antiviral state (ISGs)
How are cytosolic pathogens delt with
loaded on MHCI and activated CD8 CTLs which perform cytotoxic activity
How do CTLs cause apoptosis of infected target cells (3)
- release cytotoxic granules (performing/granzymes)
- Death ligands upregulated
- Cytokines (TNFa, INFy) released
What is inhibitory signal for NK cells
MHCI molecule on surface
What is antigenic variation
Avoid detection by altering antigens (ex. Step pneumonia)
What is latency
- viruses can enter into a non replicative state called latency in which microbe doesn’t cause disease and because there is no viral replication it is harder for immune system to find
How does HIV-1 effect the immune system
preferentially infects CD4 t cells leading to cell death and undermines helper t cell function
-leads to more opportunistic inf and cancers
