Immunology (Comp) Flashcards
Changes from immature DC to mature DC?
Immature: highly phagocytic; low CCR7 expression; low B7 expression
Mature: less phagocytic; high CCR7 expression; high B7 expression
What guides DCs to the LN?
CCR7 chemokine
What is the function of B7.1 and B7.2 on DCs?
Co-stimulatory/gives signal 2 to T cell
Location of T cell maturation/pos neg selection?
Thymus
Location of T cell clonal expansion?
LNs and spleen
Timeframe to reach peak lymphocyte expansion?
7-10 days
What happens during signals 1-2 molecularly?
1: TCR binding MHC+peptide on DC
2: CD28 on T cell binds B7 molecules on DC
Signal 1 without signal 2 leads to _____
Tolerance
MHC/T cell for extracellular pathogens?
MHC II; CD4 T cell
MHC/T cell for intracellular pathogens?
MHC I; CD8 T cell
CTLA-4 function?
Negative regulator of T cells; stops clonal expansion (more division = more CTLA-4 expression)
How do superantigens cause a massive inflammatory response?
Bypass MHC restriction to bind both MHC/TCR outside of the peptide binding groove so can activate lots of T cells
Why is MHC polymorphism important on a pop health level?
One disease won’t be able to come and wipe out the entire population in one swoop
What 2 signals are needed to activate a naive B cell?
- BCR-antigen binding
- CD40/CD40L binding (Permission to activate from Tfh)
Do B cells always need T cell help to activate?
No–certain TLRs like LPS can activate them OR so many BCRs can be activated at once that it just activates
Chemokine that B cells use to find the B cell follicle?
CXCR5
Chemokine expressed by CD4 Tfh after DC contact?
CXCR5
What do follicular DCs do?
No digestion of antigen; keeps antigen on LN surface so B cells can see them
What is the chemokine to locate B cell follicles?
CXCR5
Where do plasma cells live?
Bone marrow, medullary chords (LNs), red pulp (spleen), or tissue
What happens in the dark zone of a germinal center?
Lots of proliferation; somatic hypermutation of the BCR
What happens in the light zone of a germinal center?
Antigen driven selection of B cell clones; class switching of BCR
Monoclonal vs polyclonal antibodies?
Monoclonal – exact same protein sequence from a single B cell clone
Polyclonal – antibodies from multiple B cell clones
Function of memory B cells?
Long-lived memory; if reactivated will go through same process as naive B cell, now it just has higher affinity already. Expresses but does NOT secrete antibody
____ and ____ are major isotypes of antibody in the blood.
IgM and IgG
___ is the antibody isotype on external mucosal surfaces.
IgA
____ (antibody isotype) can be delivered to the fetus across the placenta in some species.
IgG
______ (antibody isotype) is found on epithelial surfaces on mast cells in the skin, gut, and resp tract.
IgE
What is the function of IgA at mucosal surfaces?
Neutralize pathogens and toxins
Can antibodies activate NK cells?
Yes –> Fc receptors on NK cell recognize antibody bound to pathogen; when Fc receptors cross-link it tells the NK cell to kill the target cell via apoptosis
Major determinants of how the immune system responds to something?
Size and location of pathogen
Cytotoxic immune responses use ____ and _____ cells.
NK and CD8 T cells
Goal of cytotoxic immune response?
Eliminate virally infected/metabolically stressed cells
Type 1 immune response uses ___ and ___ cells for _______ immunity.
ILC1 and Th1 cells for intracellular immunity
Goal of Type 1 immune module?
Eliminate intracellular (intra-macrophage) pathogens; activate macrophages
Type 2 immune response uses ____ and ____ cells for ___________ immunity.
ILC2, Th2 cells, barrier and mucosal immunity
Goal of type 2 immune response?
Elimination and expulsion of parasites; recruit eos, basos, and mast cells
Type 3 immune responses use ____ and ____ cells for ____________ immunity.
ILC3; Th17; extracellular immunity
Goal of type 3 immune response?
Eliminate extracellular bacteria and fungi, recruit and activate neuts
You probably won’t survive if you _______ immune system doesn’t work properly.
Innate
Function of IFN-y (gamma)?
Activate macrophages
Th1 cell function?
Activates macrophages by secreting IFN-y; also secretes TNF-a (pro-inflammatory) and IL-2 (drives CD8 CTL differentiation)
Why are CD4 cells necessary to activate CD8 cells?
CD4 Th1 cells make cytokines that induce additional DC co-stimulation (increased ability to activate CD8s)
ILCs are part of the _______ (innate/adaptive) immune response so they live in the _______.
Innate; tissue
Function of group 1 ILCs?
Make IFN-y (Th1-like cytokines)
What IL’s do Th17 cells secrete and why?
IL-17: chemokines to recruit neuts
IL-22: induces secretion of antimicrobial peptides at barrier surfaces
How do neutrophils “see” things?
Complement gradient in serum
Can a neutrophil phagocytose a capsulated bacteria?
Not without antibody–capsule polysaccharides inhibit complement fixation so capsulated bacteria are invisible to neuts
Function of group 3 ILCs?
Secrete Th17-like cytokines (IL-17 and 22)
Without T cell help, what kind of antibody response will there be?
Low affinity antibodies; usually just IgM
How do Tfh’s help B cells recognize non-peptide antigens?
The non-protein part of the pathogen must be physically connected to a peptide so it can be recognized by T cells
Type __ hypersensitivity mediates helminth immunity.
1
Function of group 2 ILCs?
Produce Th2-like cytokines; encourage Th2 development
Functions of M1 vs M2 macrophages?
M1: pro-inflammatory
M2: tissue damage/wound healing
IL-13 function?
Increased smooth muscle contractility (parasite expulsion)
IL-5 function?
Recruit and activate eos
IL-4 function?
Guides Th2 differentiation, recruit and activate M2 macrophages; inhibits secretion of macrophage pro-inflammatory cytokines
Which immune cell makes the most IL-4?
Basophils
Der p 1 function?
Cleaves occludin to enter mucosa through tight junctions
How do antibodies and mast cells work to recognize parasites?
Parasite-specific IgE binds to high affinity FcR (IgE receptors on mast cells); when the IgE binds the parasite it causes cross-linking that initiates mast cell degranulation
What is ADCC?
Antibody dependent cellular cytotoxicity – innate immune cells using antibody to recognize and kill specific pathogens
What is a self cure reaction?
An effective immune response to a large pathogen that can be identified visually
Atopic patients make a stronger ______ response.
Th2
Function of Tregs?
Promoting tolerance to prevent other T cell responses
Function of TGF-b and IL-10?
Suppress Th1 and Th2 responses
How do helminths interact with Tregs?
Helminths can directly induce Treg formation OR affect Treg products to reduce immunity.
Plasmacytoid DCs produce what?
Type 1 IFNs
Type 1 IFN function?
Stimulates cells to produce multiple interferon stimulated genes (ISGs) that target the viral life cycle & cellular protein synthesis
What do viruses do to MHC I?
Downregulate it
What does an NK cell do when it does and doesn’t see MHC I?
If it sees MHC I – it binds the inhibitory receptor on the NK cell and the NK cell isn’t activated. If the NK cell doesn’t see MHC I, it is not inhibited and it kills the cell
Define antigenic drift
Mutations in a viral genome; no co-infection
Define antigenic shift
RNA segments are exchanged between 2 viral strains
Describe the original antigenic sin.
A young person fights of a viral pathogen with proteins X and Y; when they are infected with a different strain of the same virus later and the mutated virus has proteins X, A, and B, the body will still produce the strongest response to protein X
What are the functions of perforin and granzymes in CTLs?
Perforin: pokes holes in cell membrane
Granzymes: disrupt cell machinery
