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Immunology
Molecules to Know
62
Medical
Graduate
01/13/2010

Additional Medical Flashcards

 


 

Cards

Term
CD3 and zeta protein
Definition
Signal transduction in T cells. Have ITAM's. Also stabilize TCR on cell surface. CD3 = T cell marker!
Term
CD4 and CD8
Definition
T cell co-receptors. Bind MHC Class II and I respectively.
Term
CD28
Definition
T cell costimulator receptor. Binds B7 (CD80/CD86) of APC's to receive second "go-ahead" signal.
Term
LFA-1 (CD11a/CD18)
Definition

Integrin adhesion molecule that binds to ICAM-1.

-T-cells: helps bind T cell to APC during activation.  Helps T cells home to lymph nodes via HEV.

-Endothelium: binds ICAM-1 on cells that will diapedese into tissues.

 

Term
VLA-4
Definition
"Very late antigen-4." Adhesion molecule on activated T cell expressed AFTER activation. Binds to VCAM-1 to help activated T cells get into infected tissues.
Term
CD40L
Definition

-CD40L on ag-stimulated T cell binds CD40 of APC to induce it to express B7 and secrete cytokines (IL-12) to enhance T cell differentiation.

-CD40L also triggers isotype switching in B cells

-Hyper IgM Syndrome = CD40L defect

Term
IL-2
Definition
Secreted by CD4 (and CD8) T cells after ag recognition. Binds to IL-2R (has CD25) on T cell itself to promote clonal expansion of T-cell.
Term
CD25
Definition

-High affinity part of IL-2R (alpha chain)

-CD25 alpha chain upregulated after signal transduction to increase affinity of IL-2R

Term
B7 (CD80/CD86)
Definition

Found only on pro APC's. Costimulator that gives second signal ("go-ahead") to T cell when binds to CD28.

-CTLA-4 may also bind B7 - INHIBITORY

Term
IL-12
Definition

-Secreted by macs and DC's to activate NK cells and TH1 to secrete IFN-gamma.

-Secreted by APC ("signal 3") to stimulate differentiation into TH1 cell. Release triggered by binding of CD40L to CD40.

Term
IL-4
Definition

-Secreted by TH2 cells and mast cells.

-Promotes isotype switching to IgE.

-Stimulates differentiation to TH2.

Term
IL-5
Definition
Secreted by TH2 cells, mast cells. Activates eosinophils.
Term
IFN-gamma
Definition
-Secreted by NK cells and TH1 to activate macs. -Secreted by T cells. Makes all cells upregulate Class I MHC in case of infection, stimulates some Ab responses. -Secreted by TH1 cells. Suppresses IL-4 production so no TH2 response (immune deviation).
Term
TGF-beta
Definition

-Secreted by CD4 T cells and many cancer cells. -Inhibitory cytokine-generally inhibits T cell proliferation.

-Differentiation and activation of Tregs.

Term
TH1 Cells
Definition
Secrete IFN-gamma. Activate macrophages for killing, and increase Ab and complement secretion so opsonization can facilitate killing by macs.
Term
TH2 Cells
Definition
Secrete IL-4 to stimulate B cells to make IgG and IgE (allergic response). Secrete IL-5 to activate eosinophils - protect against helminths.
Term
TH17 cells
Definition
Secrete IL-17. Play big role in inflammatory diseases (ie. arthritis).
Term
CTLA-4
Definition
T cell accessory molecule that binds to B7 and causes T cell to respond LESS well to APC.
-Gives T cell activation system balance
-Important for inducing anergy to self-ag's
Term
TNF-alpha and IL-1
Definition
Secreted by macrophages in tissues that have engulfed ligands. Stimulate upregulation of selectin (CD62-E) on endothelium, AND integrins on leukocytes. FEVER.
Term
Leukocyte Adhesion Deficiency (LAD)
Definition
Missing CD18, which is partnered with the following to make integrins: -CD11b/Mac1/CR3 - no homing of macs or neutrophils to tissues -CD11a (LFA-1) - no homing of T cells to lymph nodes -CD11c/CR4 - defect in DC activation
Term
X-SCID
Definition
Takes out most of acquired immune system AND NK cells. Cause of death = No NK cells
Term
IL-8
Definition
All cells can make it. Attracts neutrophils to site of infection.
Term
IFN-alpha and IFN-beta
Definition
Alpha - DC's, macs.
Beta - Fibroblasts.
-Puts all cells in anti-viral state, upregulates MHC Class I
-Activate NK cells
Term
MHC Class I Structure
Definition
HLA A, B, C.
-Beta 2 microglobulin
-Alpha 1 and alpha 2 = peptide binding cleft
-Alpha 3 = CD8 binding site
Term
MHC Class II Structure
Definition
-HLA DP, DQ, DR
-Alpha 1 and beta 1 = peptide binding cleft
-Beta 2 = CD8 binding site.
Term
IL-7
Definition
Secreted by stromal cells in thymus/BM. Proliferation of immature T and B cells with lots diff ag receptors.
Term
S1PR
Definition
Sphingosine-1-phosphate receptor. Expressed on activated T cells that need to travel in the BLOOD.
Term
CD62-L (L-selectin)
LFA-1
Definition
Homes T cells to HEV in lymph node.
Term
CCR7
Definition
Homes DC's and T cells to the T cell zone of lymph nodes and spleen.
Term
CD103
Definition
Targets intraepithelial lymphocytes and Tregs to gut mucosa.
Term
IL-10
Definition

-Made by TH2 cells and macs to inhibit activated macs. 

-Secreted by TH2 cells to inhibit TH1 (immune deviation).

-Secreted by Tregs to inhibit DC secretion of IL-12, therefore inhibiting TH1 cells.

Term
CD21 (CR2) and CD19
Definition
Costimulation of B cells (signal 2). CD21/CR2 bind C3d covered microbes.
Term
IgM
Definition
-Bound to naive B cells.
-Primary response, pentameric, low affinity
-Activation of Classical Complement Pathway
-Intermediate levels in blood
Term
IgD
Definition
-Membrane-bound ONLY. B2 cells but not B1.
-Very low levels
-Necessary for isotype switching
Term
IgG
Definition

-Secondary response, highest levels in blood, monomeric -Neutralization -Opsonization -Activates Classical Complement Pathway -ADCC -Neonatal immunity - transferred to placenta via FcRn -Feedback inhibition of B cell activation (CD32)

-IFN-gamma induces switch to IgG

Term
IgA
Definition
-Secreted Ab only, monomer/dimer/trimer
-Mucosal immunity - agglutinates/neutralizes microbes
-Breast milk
-Isotype switching induced by TGF-beta
Term
IgE
Definition
-Secreted Ab only
-Isotype switching induced by IL-4 (TH2 cells)
-Bound WITHOUT ag to mast cells and eosinophils so get IMMEDIATE hypersensitivity and worm killing!
Term
CD32 (FcgammaRII)
Definition
Inhibitory B cell receptor. Excess IgG bound to ag binds CD32 and send negative signals to B cell - turns off Ab production.
Term
CD64 (FcgammaR1)
Definition
FcR on macs and neutrophils. Binds Fc region of IgG to phagocytose opsonized ag's.
Term
CD16 (FcgammaR3A)
Definition
NK cells. Ab Dependent Cytoxicity (ADCC).
Term
C3b
Definition
-Opsonin. Binds CR1 on phagocytes.
-Component of C3 and C5 convertases
Term
C3d
Definition
Binds CR2 (CD21) to activate B cells.
Term
C3a, C4a, C5a
Definition
All stimulate inflammation! All are chemokines that attract leukocytes.
Term
T regulatory cells (Tregs)
Definition

-Self-reactive cells NOT killed by neg selection in thymus or in periphery

-Foxp3, IL-2, and TGF-beta stim Treg development

-High constitutive levels of CD25 (IL-2R)

-Development and fxn depend on Foxp3 (TF)

-Inhibit prolif, activation, and effector fxn of T cells!

-Direct contact - DC express less B7 and IL-12

-IL-10 decreases IL-12 secretion by DC's so no TH1 cells

-TGF-beta generally inhibits T cell prolif

Term
C1 INH
Definition
C1 Inhibitor. Blocks C1q to inhibit Classical Complement Pathway.
Term
DAF
Definition
Decay-accelerating Factor. Membrane protein expressed on all cells, esp. RBC's. Prevents formation of C3 convertase!
-Alt Pathway - prevents binding of Factor B
-Classical Pathway - prevents binding of C4b
Term
Factor I
Definition
-Cleaves C3b to iC3b (opsonin) and C4b
-Needs help from membrane-bound cofactors (MCP, CR1, Factor H)
Term
MCP
Definition
Membrane Cofactor Protein. Helps Factor I cleave C3b and C4b to inhibit formation of C3 convertase.
Term
Factor H
Definition
Displaces Factor B so that Factor I can cleave C3b and prevent formation of C3 convertase.
Term
CD59
Definition
Membrane-bound protein on host cells that prevent binding of C9 - no MAC can kill it!
Term
Hereditary Angioneurotic Edema
Definition
Defect in C1 INH. Classical Complement Pathway activated more often than should be --> release of inflammatory mediators (bradykinin) --> edema.
Term
Paroxysmal Nocturnal Hemoglobinuria
Definition
Defect in DAF and MCP on RBC's. No regulation of complement cascade --> hemolysis.
-No DAF - C3b buildup on RBC's
-No MCP - no Factor I to inactivate C3b to iC3b
Term
Factor I Deficiency
Definition
-Increased bacterial infections because no production of iC3b for opsonization and B cell activation
-Decreased C3 because nothing is preventing cleavage of C3 to C3b!
Term
Autoimmune Hemolytic Anemia (Rh Disease)
Definition
-Type 2 Hypersensitivity
-Ab's against RBC proteins (Rh, I protein)
-Opsonization and phagocytosis of RBC's
-Hemolysis, anemia
Term
Autoimmune Thrombocytic Purpura
Definition
-Type 2 Hypersensitivity
-Ab's against GpIIa/IIIb on platelets
-Opsonization and phagocytosis of platelets
-Bleeding
Term
Pemphigus Vulgaris
Definition
-Type 2 Hypersensitivity
-Ab's against demosglein-3 (desmosomes)
-Ab-mediated activation of proteases, disruption of intercellular adhesions
-Skin bullae, blisters, erosion of skin
-Ashkenazi Jews, HLA D4/DQ3
Term
Goodpasture's Syndrome
Definition
-Type 2 Hypersensitivity
-Ab's against BM proteins in glomeruli and alveoli
-Complement and Fc mediated inflammation
-Nephritis, lung hemorrhages
Term
Acute Rheumatic Fever
Definition
-Type 2 Hypersensitivity
-Ab's against Strep cross-react with heart
-Inflammation, mac activation
-Myocarditis, arthritis
Term
Myasthenia Gravis
Definition
-Type 2 Hypersensitivity
-Ab's against Nm receptors at NMJ's
-Blocking of ligand, complement fixation, downreg of receptors
-Muscle weakness, paralysis
Term
Graves' Disease
Definition
-Type 2 Hypersensitivity
-Ab binds to TSH receptor and STIMULATES it
-Hyperthyroidism! Thyroiditis but no tissue destruction
Term
Hashimoto's Thyroiditis
Definition
-Type 2 Hypersensitivity
-Ab's against thyroglobulin and TPO prevent production of T3/T4
-Hypothyroidism! Thyroiditis AND tissue destruction
Term
Pernicious Anemia
Definition
-Type 2 Hypersensitivity
-Ab's against GIF
-No absorption of Vit B12, macrocytic anemia, abnormal erythropoeisis
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