Immuno Flashcards
What part of the spleen is non-immunologic? Functions?
Red pulp; filter debris from blood, convert Hgb to bilirubin, reutilize Fe
What part of the spleen is immunologic? Where are T cells found? Where are B cells found?
White pulp; PALS around central arteriole; primary and secondary follicles
Main product of primary and secondary follicles (spleen)?
Antibodies, especially IgM
How do T cells acquire T cell receptor (TCR)?
In the thymus, by interacting with cortical thyme horses like thymosin, thymulin, and thymopoietin
Where are M cells found? What pathogen can transverse them? Where does it then reside?
Overlying Peyer’s Patches in intestine; Salmonella; macrophages
What recognizes LPS?
TLR-4
What pathogens possess double-stranded RNA?
Viruses (uniquely)
What do interferons do, broadly?
Confer resistance to adjacent, uninfected cells
What can NK cells do?
Target and kill virally infected and cancer cells
What cells display MHC I?
All nucleated cells in the body
What cytokines are seen early on during viral infection
IFN-a, IFN-b, TNF-a, IL-12
What 2 cellular changes elicit targeting from NK cells?
Loss of MHC I, over expression of stimulatory ligands
How do NK cells and CD8+ T cells provide “reciprocal coverage”?
NK cells target cells that stop expressing MHC I, whereas CD8+ cytotoxic T cells use MHC I to recognize epitopes
What interferons are anti-viral? What effect do they have?
Type I interferons: IFN-a and IFN-b; incr. expression of MHC class I
What interferons are anti-bacterial? What effect do they have?
Type II interferons: IFN-gamma (produced by leukocytes); incr. expression of MHC I and MHC II
Describe the interferon response to virally-infected cells
IFN-a and IFN-b: induce resistance to viral replication in cells, incr. expression of ligands for NK cell receptors, activate NK cells
IL-7 function
B cell survival
What is CD25? Where is it found and what is its function?
Surface molecule on T cells; double negative T cells; IL-2 receptor, important for development
What is CD3 responsible for?
Intracellualr signaling (on T cells); necessary for TCR to bind MHC (functional receptor includes TCR + CD3)
What is AIRE? What does it do?
AutoImmune REgulator transcription factor; forces extrathymic proteins to be expressed in the thymus so that T cells that react with self components with a high affinity will be deleted
Define toxoid
Inactivated toxin
What happens in the “dark zone” of the germinal center wishing secondary lymphoid tissues?
Proliferation of B cells, somatic hypermutation
What happens in the “basal light zone” of the germinal center wishing secondary lymphoid tissues?
Positive selection for binding to antigen on follicular dendritic cells
What happens in the “apical light zone” of the germinal center wishing secondary lymphoid tissues?
Production of memory B cells and plasma cell precursors, class switching
Which immunoglobulins are polymers?
IgM (pentamer), IgA (dimer)
Which complement proteins are not involve in the alternative pathway?
C1, C4
IgG function
Most abundant, secondary response, IgG1 and IgG3 are cytophilic, classical complement activation, crosses placenta
IgM function
Primary response, classic complement system, produced in blood borne infections
IgA function
The secreted immuglobulin: present in tears, saliva, feces, breastmilk; functions in neutralization
IgE function
Binds Fc receptor on Mast cells and basophils, atopic diseases (allergy and asthma), immunity to helminths
Where is B7 found and what does it do?
Co-stimulatory molecule on dendritic cells binds CD28 on naive T cells for the 2nd step of activation
Where is CD28 found and what does it do?
Co-stimulatory molecule on T cells binds B7 on dendritic cells for the 2nd step of activation (can also bind CD80, a member of B7 family)
2 steps of T cell activation
1st: recognition of MHC-Ag complex by TLR
2nd: “co-stimulation” binding of dendritic B7 or CD80 to T cell CD28
IL-2 function
“Drives T cell division” - IL-2 acts in an autocrine and paracrine fashion to incr. production of IL-2 and expression of IL-2 receptor (CD25); in addition activated T cells incr. the affinity of their IL-2 receptors
Th1 cell responsibilities
Make macrophages better killers via IFN-gamma (also secrete IL-2), produce opsonizing Ab such as IgG, “intracellular killers” of intracellular bacteria and viruses, and a smaller role in B cell activation
Th2 cell responsibilities
Help B cells make Ab (via IL-4 and IL-5) by expressing CD40 in response to antigen recognition, which binds CD40 on B cells, causing proliferation and differentiation into plasma cells (also induce mast cells and basophils = allergy connection)
Describe reciprocal inhibition by Th cells
Th1 secretes IFN-gamma which inhibits Th2 cells; Th2 cells produce IL-10 which inhibits production of IFN-gamma by Th1 cells
Which cytokines are classified as lymphotoxins? What cells produce lymphotoxins? What is their effect?
LT, TNF-b; Th1 and CTL cells; activation and induction of NO production in macrophages
IL-3 function
Growth factor for progenitor hematopoietic cells
GM-CSF function
Incr. production of granulocytes, macrophages and dendritic cells
What type of T cell retains its memory better?
CD8+ cytotoxic T cells
Th1 cell cytokine profile
IFN-gamma, IL-2, IL-3, TNF-a, TNF-b, GM-CSF, LT
Th2 cytokine profile
IL-4, IL-5, IL-9, IL-10, IL-13, TGF-b
Cytotoxic T cell cytokines profile
LT, IFN-gamma
What cells display MHC class II?
Macrophages, dendritic cells, B cells, and epithelial cells of the thymus
Describe the structure of MHC class I
Homotrimer (3 alpha chains) with beta-2 microglobulin attached for stability
Describe the structure of MHC class II
Heterodimer (alpha and beta chains)
TAP function
Allows cytoplasmic antigens into the ER so they can be loaded onto MHCI
What MHC type presents cytosolic antigens?
MHC class I (remember association with viruses)
What MHC type presents phagocytosed antigens?
MHC class II
What MHC type presents antigens ingested by receptor-mediated endocytosis (e.g. by B cells)?
MHC class II
Name a virus that attacks TAP
HSV-1
CLIP function
Stabilize MHCII and prevent binding of “wrong” peptide
HLA-DM function
Facilitate swap of CLIP for antigen on MHCII
