Term
| Properties of the Acquired Immune System |
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Definition
1) Specificity
2) Can respond to a diversity of antigens
3) Self/nonself recognition
4) Memory of previous invaders
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Term
| Crossover between Innate and Acquired Immunity |
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Definition
| Innate immune responses help form adaptive immune responses and adaptive immune responses utilize the machinery of innate immunity for effector function |
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Term
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Definition
B cell/antibody-mediated immune response; does not require antigen presentation
B cells mature in lymph nodes and spleen; co-stimulated by binding with antigens and secreted products from Th cells to fully activate the B cell
B cell clonal populations of effector (plasma cells containing soluble antibodies) and memory (contain membrane-bound antibodies, longer lifetime and more rapid/heightened response) develop |
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Term
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Definition
T cell/antibody-mediated immune response
T cells are formed in bone marrow and mature in the thymus
Antigen Presentation: Activation of T cells (binding between TCR and antigens) |
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Term
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Definition
Pathway for exogenous antigens
T(h) cells: express surface protein CD4
MHCII: Antigen binds to alpha and beta 1
antigens enter host cell through phagocytosis, degraded into peptide fragments during endocytosis
Fragments bind to MHCII molecules in endocytic vesicles, transported to cell membrane
T(h) cell produces cytokines that stimulate the humoral response, T(c) pathway
Common result of directly implanted biomaterial |
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Term
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Definition
Pathway for endogenous antigens (produced after alteration of a native cell due to toxic/carcinogenic properties of the biomatl)
Antigens first degraded into peptides w/in the cytoplasm, bind to MHCI in the RER, transported to cell membrane
MHC1- Express surface protein CD8; antigen binds to alpha 1 and 2 regions (found on all nucleated cells)
T(c) cell is stimulated by T(h) cytokines to develop into a CTL, which lyses infected self cells by secreting porforins and cytotoxic enzymes
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Term
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Definition
| The specific site on an antigen recognized by an antibody |
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Term
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Definition
| A low MW substance that combines with a larger molecule to produce an amplified immune reponse |
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Term
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Definition
| A substance that non-specifically enhances the immune response to antigens, possibly by increasing their uptake by phagocytic cells or promoting time the antigen remains in the body |
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Term
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Definition
IgG:Binds 2 antigens; 75% of antibodies
IgE: Binds 2 antigens; major component of the allergic reaction
IgA: Dimerization (J chain); able to bind 4 antigens; takes part in agglutination reaction
IGD:Binds 2 antigens
IGM: Pentamerization (J chain): Able to bind 5 antigens at once |
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Term
4 mechanisms of antibody action
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Definition
1) Agglutination: Clumping together of antigens
2) Precipitation: Antigen becomes insoluble
3) Neutralization: Antibody covers the active site
4) Lysis: Antibody bursts infected cell |
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Term
| Functions of the Complement System |
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Definition
1) Amplification of antibody reaction
2) Lysis of foreign cells, bacteria, viruses
3) Opsonization (C3b attached to foreign surface recognized by receptors on phagocytes)
4) Immune Clearance |
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Term
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Definition
C1q binds to antibody-antigen complex or directly to some pathogen surfaces
C1q binds to 2C1r and 2C1s zymogene
Binding of C1q heads to pathogenic surface initiates C1r enzymatic activity, cleaving of C1s to generate serine protease
Activated C1s cleaves C4 to C4a and
C4b (C4b binds to microbial surface, C4a becomes a chemoattractant)
C4b binds C2, which is cleaved by C1s into C2b and C2a (C2b complexes with C4b to form C3 convertase, C2a becomes a chemoattractant)
C3 convertase cleaves C3 into C3a and C3b (C3b complexes with C3 convertase to form C3/C5 convertase capable of cleaving many C3 to amplify the response, C3a becomes a chemoattractant [inflammatory mediator])
C3/C5 convertase cleaves C5 into C5a (most important chemoattractant and C5b (initiates MAC formation by combining with C6/7/8 and a ring of C9 to create a pore in the cell membrane)
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Term
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Definition
Initiated by spontaneous plasma C3 hydrolysis
C3b is produced at a sig. rate by spontaneous cleavage (C3 tick-over) through spontaneous C3 thioester hydrolysis to form C3(H20), binding factor B. D plasma protease cleaves B to form C3(H2O)Bb (a fluid C3 convertase that cleaves C3 to a and b); most C3b are inactivated by H20 |
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Term
| Terminal Complement Components |
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Definition
C5 convertase is formed when a large number of C3b of the pathogen surface bind to C4b2b or C3bBb; C5b initiates assembly of the terminal complement component
Activity: C5a>C3a>C4a
C5a activates mast cells and degranulates mast cell mediators; histamine and TNF-alpha induce inflammation; can also enhance phagocytosis of opsonised microorganisms |
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Term
| Decay-accelerating factor (DAF) |
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Definition
| Membrane protein that displaces Bb from C3b and C2b from C4b |
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Term
| Hypersensitivity/Allergic Response |
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Definition
Type 1- IgE mediated (occurs after 2nd exposure; mast cells and basophils release soluble factors) example: latex allergies
Type 2- antibody mediated (antibody destroys cells and platelets by activating the complement system)
example: infusion of an incorrect blood type
Type 3- Immune Complex Mediated (Days-> weeks after original exposure); activates complement system, leads to massive influx of neutrophils
Example: Autoimmune Diseases e.g. diabetes/Lupus
Type 4- Cell mediated; delayed (27-72h post-exposure) response; usu. starts at 2nd exposure; no antibodies; T(h) cells release cytokines that activate macrophages or T(c) cells
Example: response to a metallic biomatl |
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