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63 Cards in this Set
- Front
- Back
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IgG
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-most prevalent
-crosses the placenta -activates complement via the alternative pathway |
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This antibody crosses the placenta?
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IgG
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IgM
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-early in immune response
-pentamer- ten binding sites- avid -joined by a J chain -fixes complement |
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IgA
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-secretory
-monomer and dimer (J chain) -no complement activation |
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IgE
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-primary trigger of allergic reactions
-occurs in parasitic infections (opsonizes the parasite) -Fc region binds to receptors on mast cells and basophils |
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IgD
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-mystery immunoglobulin
-exists on the surface of B cells as a receptor |
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epitope
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-antibody binding site on an antigen for a specific antibody
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somatic recombination
(combinational diversity) |
random arrangement of different V,D, and J alleles
-process is mediated by recombinase enzymes (RAGS) |
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junctional diversity
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mutations to the V,D, and J joining sites, usually by the addition of a nucleotide
-mediated by terminal deoxyribonucletidyl transferase |
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Affinity Maturation
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-after antigen binding/stimulation
-affinity maturation of the antigen receptor during B cell proliferation occurs from random mutations in the hypervariable region -higher affinity Ig results |
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Isotype switching
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-occurs in response to Th cytokines, resulting in memory B cells
-the membrane Ig becomes very high affinity IgG, IgA, or IgE |
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B stem cell
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-no Ig
-unrearranged Ig genes |
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Pre-B cells
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-cytoplasmic u chains
-H chains are rearranged |
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Immature B cell
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-low concentration of surface IgM
-L chain genes are rearranged |
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Mature B cell
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membrane IgM and IgD
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Precipitin Reaction
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various amounts of a soluble antigen are added to a fixed amount of serum containing antibody.
-equivalence: large lattices of antigen and antibody are formed by cross-linking |
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Zone of Equivalence
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-At just the right Ag and Ab concentrations maximum crosslinking occurs resulting in large immune complexes that precipitate
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Immunoblotting (Western Blot)
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-used for detecting antibodies to an array of antigens
-eg HIV diagnosis -electrophoresis of antigens followed by transfer onto porous membrane -membrane reacted with Ab specific for proteins -reaction with anti-Ab conjugated with substrate -enzyme substrate is usually colored |
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ELISA
(Enzyme-linked immunosorbent assay) |
Ag-Ab complex detected by color-changing enzyme linked to second antibody
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Agglutination
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-antibody molecules binding to antigens on the surfaces of adjacent particles, causing them to clump together
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Hemagglutination
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Antibody mediated agglutination of RBC
-example: test for determining A,B,O blood type |
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Coomb's Test
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-test for erythroblastosis fetalis
-agglutination test for the presence of maternal antibody to Rh determinants on fetal RBC |
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The Classical Pathway
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C1 complex
-C1q binds to antibody -C1q crosslinking activates C1r, which activates C1s -C1s hydrolyzes C4 to C4a and C4b and C2 to C2a and C2b -C3 convertase= C4b2b |
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The mannose-binding lectin pathway
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-like the classical pathway without Ab
-Mannose binding lectin (MBL) is activated by binding to mannose-containing structures on microbes -activated MBL activates MBL-associated proteinase 1 and 2 (MASP-1,2) MASPS hydrolyze C4 and C2 forming C3 convertase C4b2b |
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Alternative Pathway
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-activated on microbial surfaces
-C3 convertase: C3bBb -does not depend on pathogen binding protein for initiation -initiated through spontaneous hydrolysis of C3 forming C3b |
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C3 tick-over
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large amounts of C3b that is spontaneously formed in the 'fluid phase
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Steps of the Alternative pathway
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-hydrolysis of C3 by water generates C3i, which binds factor B
-hydrolysis of B by factor D generates C3iBb (fluid-phase C3 convertase) |
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alternative pathway C3 convertase
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C3bBb
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Membrane Attack Complex
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-initiated by C5 convertases
-cleavage of C5, release C5b -C5b binds to C6, forming C5b6 complex -C5bC6 mediates the insertion of C7 and C8 into the target membrane C5bC6C7C8 mediates the insertion of multiple C9 subunits that form a pore in the membrane -results in lysis of the target cell |
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Decay Accelerating Factor (DAF)
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-displaces Bb from C3b
(stopping alternative pathway) -dissociates 2b from 4b (classic/lectin pathway) |
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C4b binding protein (C4b BP)
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binds C4b, displacing 2b
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CD59
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-prevents formation of MAC complex
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Factor I
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hydrolyzes C4b and C3b (MCP and CR1 are cofactors)
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MHC class II gene clusters
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DP, DQ, DR
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MHC class I gene clusters
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A, B, C
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MHC I
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-expressed by all nucleated cells and platelets
-expressed with peptide to CD8 cells |
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MHC II
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-expressed with peptide to CD4 cells
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MHCII pathway
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-Class II proteins delivered via calnexin from ER to ribosomes
-MHC II dimers assemble and peptide binding site is protected by invariant chain (Ii) as class II protein moves from ER to golgi -endosome with degraded Ag fuses with exocytic vesicle forming class II compartment (MIIC) -Li is hydrolyzed to CLIP -vesicle fuses with membrane exposing MHC II with peptide |
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MHC I pathway
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-processing of endogenous Ags
-peptide fragments are transported by TAP-1 and TAP-2 to the ER -MHC I protein associated with B2-microbglobulin |
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T cell Receptor Diversity
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β chain has V,D,J
α chain has V, J -RAG -Junctional diversity |
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T cell maturation
Positive selection |
-cells that can recognize self MHC are selected to continue
-double positive cells undergo positive selection |
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T cell maturation
Negative selection |
-retained only if they do not recognize self antigens
-single positive cells undergo negative selection |
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LFA-1
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on T cells
-binds ICAM-1 on APC |
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CD28
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-on T cells
binds B7.1/B7.2 on APC -secondary signal -after activation is replaced by CTLA-4, which downregulates the T cell |
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Affinity
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the strength of the bond (epitope/paratope
-the sum of the attractive and repulsive forces |
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Avidity
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the strengths of all bonds (all paratopes)
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IL-12
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promotes Th1 differentiation
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IL-4
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promotes Th2 differentiation
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IL-1
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-main source: macrophages, lymphocytes, endothelial cells
-inflammation |
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IL-2
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-secreted by T cells
-induces T cell proliferation "T-cell growth factor" -activates NK cells and B cells |
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IL-3
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-secreted by T cells
-stimulates hematopoiesis |
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IL-4
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-secreted by T cells
-Th2 polarization -stimulates IgE |
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IL-5
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-secreted by Th2 cells
-enhances IgA synthesis |
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IL-4
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Promotes Th2 polarization
IgE isotype switching |
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IL-5
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Induces IgA isotype switching
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IL-6
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activates osteoclasts
-stimulates platelet formation |
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IL-12
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promotes Th1 polarization
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IL-18
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IFN γ inducing factor
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Adhesion molecule on leukocytes that binds to ICAM-1 on endothelial cells
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LFA-1
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TNFα inducible adhesion molecule on endothelial cells that binds a glycoprotein on leukocytes during 'tethering'
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E-selectin
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Adhesion molecule on lymphocytes that binds to extracellular matrix proteins and VCAM-1 on endothelial cells
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VLA-4
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Adhesion molecule on T cells that binds LFA-3 on APCs
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CD2
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T-cell receptor associated protein associated with signal transduction
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CD3
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