Immunology midterm Flashcards
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IL-2
Source - Thp, Th0, Th1
- Growth factor for T cells
- Enhances NK cell cytotoxicity
- Plays a role in pCTL to CTL differentiation
IL-1 and TNF (synergistic)
Source: IL-1 - MAC
TNF - MAC, Th1
- Play an important role in inflammation
- Activate (or enhance activation of) macrophages to secrete cytokines (IL-1, 6, 12, TNF) and chemokines (IL-8 and MCP-1)
- Activate endothelial cells leading to de novo expression of ICAM-1, VCAM-1, and E-selectin, and enhanced expression of ICAM-2. Also induce endothelial cells to secrete chemokines IL-8 and MCP-1
- Systemically, IL-1 and TNF act on hypothalamus to induce fever and play a key role in lowering of blood pressure leading to shock
IL-3
Source - T cells
- Hematopoiesis - important for both myeloid and lymphoid progenitor cell development
IL-4
Source - mast, Th0, Th2
- Required to isotype switch to IgE
- Downregulation of Th1 cytokine production
- Downregulation of iNOS (not as effective as TGFB)
- Shifts Th0 response to Th2 phenotype
IL-5
Source - mast, Th2
- Hematopoiesis - differentiation of eosinophils
- Chemotactic for eosinophils; recruiting eosinophils to tissues
- Activation of eosinophils
IL-6
Source - MAC, Th2
- Stimulus for the secretion of C-reactive protein from hepatocytes (inflammation)
- In the presence of TGFB, IL-6 plays a role in the differentiation of Thp cells to Th17
IL-7
Source - BMS
- Hematopoiesis - role for B and T cell differentiation. Bone marrow and thymus
IL-8 (CXCL8)
Source - mac, endothelial cells
Chemotactic for neutrophils
IL-10
- Downregulates IL-12 secretion by dendritic cells and macrophages (leads to downregulation of Th1 cytokines)
- Downregulates iNOS but not as effective as TGFB
- Inhibitory molecule
IL-12
Source - MAC, den
- Activates NK cells to secrete IFNy (enhanced if either IL-15 or IL-18 is present)
IL-13
Source - Th2
- In lung, mediator of allergic asthma
- Plays a role in helminth infections (nematodes - round worms)
IL-15
Source - MAC, den
- Plays a role (along with IL-12) in inducing NK cells to secrete IFNy
- Shares many in vitro biological activities with IL-2
- Role in inflammation
- Chemo attractant for T cells, NK cells, and neutrophils
IL-17
Source - Th17
- Functionally, IL-17 induces expression of proinflammatory cytokines and chemokines from a wide range of cells (eg IL-6, IL-8, GM-CSF, G-CSF and metalloproteinases from macrophages and other cell types)
- Autoimmune disorders if Th17 cells specific for self antigen
- IL-17 is chemotactic for neutrophils
- Plays a key role in fungal infections and in extracellular bacterial infections
IL-21
Source - Th17
- Growth factor (amplification) of Th17 cells
IL-22
Source - Th17
- Proinflammatory - has been shown to be elevated in several inflammatory conditions (eg rheumatoid arthritis and psoriasis)
IL-23
Source - den
- Role in differentiation of Thp cells to Th17 in the presence of TGFB and IL-6 or IL-1
- Proinflammatory cytokine that is composed of two subunits (p19 and p40). The p40 subunit is common to both IL-12 and IL-23
- Elevated in multiple sclerosis, psoriasis, and Crohn’s disease
IL-33
Source - mast, other
- Activates mast cells
- IL-33 is upregulated in intestinal parasite infection
- Th2 cells have receptors for IL-33. Fxn???
- IL-33 suggested to be member of the alarmin family, molecules that are released upon tissue necrosis. IL-33 is released when endothelial cells or epithelial cells undergo damage/necrosis. As such IL-33 can trigger multiple immunological processes as a result of trauma or infxn (eg activate mast cells). Some immune cells can secrete alarmins without developing necrosis.
- Dysregulated IL-33 contributes to asthma, arthritis, and inflammatory bowel disorder
GM-CSF
Source - Mac, T cells
- Role in hematopoiesis; role in differentiation of myeloid progenitor to GM progenitor
- Role in mobilization and activation of dendritic cells
G-CSF
Source - mac
- Role in hematopoiesis; role in differentiation of GM progenitor to granulocyte/neutrophil
M-CSF
Source - mac
- Role in hematopoiesis; role in differentiation of GM progenitor to granulocyte/neutrophil
TGFB
Source - Th2
- Downregulation of iNOS
- Critical for differentiation of Th0 cells to a/i Tregs
- In the presence of IL-6 or IL-1 and IL-23 -> differentiation of Thp cells to Th17
IFNy
Source: NK cells, Th0, Th1
- Activate iNOS
- Enhances activation of NADPH oxidase
- Downregulates production of Th2 cytokines
- Critical for Th0 differentiation to Th1 phenotype
- Along with IL-2, promotes pCTL to CTL differentiation
- Enhances expression of Class I MHC on nucleated cells
- Enhances expression of Class II MHC on antigen-presenting cells
TNF alone
Source - MAC, Th1
- TNF enhances NADPH oxidase activity
- TNF: role in the activation of inducible nitric oxide synthase
MCP-1 (CCL2)
Source - mac, endothelial cells
Chemotactic for monocytes
Eotaxin (CCL11)
Source - epithelial cells, fibroblasts
Chemotactic for eosinophils
IFNa and IFNB
Source - virally infected cells, particularly double stranded RNA viruses
- Triggers production of enzymes (2’5’ oligoadenylate synthetase)
- Inhibition of T cell proliferation
- Increase expression of Class I MHC on nucleated cells
Cytokines and chemokines secreted by macrophages
Cyto: IL-1,6,12,18, TNF
Chemo: IL-8 (CXCL8) -> neutrophils and MCP-1 (CCL2) -> monocytes
Recall steps for B cell humoral immune response to protein antigen
.
C3a
Anaphylatoxin, causes degranulation of mast cells and basophils -> histamine release, degranulation
C4bp
Binds/competes with C4b (ONLY IN CLASSICAL COMPLEMENT PATHWAY)
C5a
Anaphylatoxin. Also chemotactic for neutrophils
Properdin
Stabilizes C3 convertase in alternative complement pathway by increasing t1/2 by 6-10 fold. Enhances complement reaction
C1 INH
Inhibits C1. Protease inhibitor and is most important physiological inhibitor of plasma kallikrein
Deficiency of C1 INH permits plasma kallikrein activation -> production of vasoactive peptide bradykinin
IgA
- Monomer, dimer, or trimer
- t1/2 = 1 week
- Located in MALT, tears, sweat, saliva
- Secreted for immuno surveillance
- Major in milk and colostrum
IgD
- Mostly membrane-bound
- Expressed on naive B cells
- Low detectable serum levels -> products of B cell death
IgE
- Monomer
- Mostly bound to FcER -> barely detected in serum
- Mast cells and basophils
- X-linking -> release histamine
IgG (1, 2, 3, and 4)
- Monomer
- 75% if total antibodies
- Longest t1/2! = 3 weeks
- Crosses placenta and some colostrum
1. Opsonization (phagocytes)
2. ADCC (NK cells) via target cell-bound IgG binding low affinity FcyR receptors on NK cells
3. Complement activation (C1)
4. Neutralizes viruses and toxins by binding Ags and inhibiting Ag’s ability to bind cell surface receptor
IgG1 in highest conc, Ig4 lowest. IgG3 t1/2 is one week, but most effective CCP activator of all IgG subtypes. IgG4 doesn’t activate complement at all or bind to FcyR. All IgG subtypes cross placenta
IgM
- Free pentameter with J chain or membrane-bound monomer
- 15% of total antibodies
- t1/2 = 1 week
- Only isotype expressed on immature B cells
- Best activator of classical pathway
- Isohemagglutinins
Summary of thymic events
- Expression of CD2
- Somatic recombination of beta chain
- Expression of pre-TCR-CD3 complex (CD3, preTa, and B chain; requires prior somatic recombination of beta chain)
- Expression of both CD4 and CD8 on the same cell
- Somatic recombination of alpha chain
- Expression of TCR-CD3 complex
- SELECTION-SCREENING (positive, negative, death by neglect)
- Lineage selection
- Cross into medulla
- Negative selection (this time, APCs are from bm, not thymus)
- Exit to periphery
- Effector cells that exit include CD4+ Thp, CD8+ pCTL
Characteristics of membrane immunoglobulin (B cell antigen recognizing receptor)
mIg associated with CD79 a + B (Ig a + B) heterodimer. 2 light chains - k or l and 2 heavy chains - m or d
Armamentarium of NK cells
Lytic granules containing perforin and granzymes
DAMPs examples
MSU - monosodium urate crystals, chol crystals, skin irritants/UVB radiation, gluc-derived ROS/elevated extracellular gluc, FFAs, silica dust
Endogenous antigen processing
Class I MHC!!!
- Microorganisms present in cytoplasm, but not enclosed within vacuole degraded by proteosome
- Peptide fragments from proteosome bind to transporter of antigen processing (TAP) proteins
- TAP brings fragments to ER
- In ER, fragments come into contact with class I MHC molecules -> form complex
- Complexes are released from Golgi into vesicle that fuse with cell membranes
- Ag peptide/class I MHC is displayed on cell surface