week 11 Flashcards
antibodies (structure)
- Key to immunological specify
- Structure
○ 4 polypeptide chains
○ 2 large heavy chains
○ 2 smaller light chains
Bound by disulfide bonds
- Structure
antibodies (constant and variable reasons, and which class)
- Constant and variable regions
○ Defined by constant regions of conserved aa sequences
○ Heavy chain defines antibody class (isotope)
○ Each class is common to a species
§ Isotope: defines various heavy chains of a species
§ Allotype: differences in the constant region shared by some but not all members of a species
Idiotype: differences in the hypervariable region within an individual
IgG antibody isotope
- Simplest, smallest, most abundant antibody in blood and tissue fluids
- Monomer with 4 classes
Binds and opsonizes microbes (allows phagocytes to grab easier), neutralizes viruses, activates classical complement pathway
- Monomer with 4 classes
IgA antibody isotope
- Secreted antibody of mucosal surfaces
- Found as a dimer linked by disulfide bonds to the j-chain protein
- Secretory piece is wrapped around both molecules during secretion
Secretory IgA (slgA) found in tears, breast milk, mucosal surfaces: can binds 4 antigens (same one)
IgM antibody isotope
- Found as monomer on B-cells’ surfaces (part of receptor)
- Commonly found as pentamer held together by J-protein
- First antibody isotope detected during course of infection
Can bind 10 antigens
IgD antibody isotope
- Present in trace amounts in blood
- Exists in monomeric form on B-cell surfaces
- Plays role in B-cell activation
Function not well understood
IgE antibody isotope
- In trace amounts in the blood
- Found on surfaces of mast cells and basophils
Amplify body’s response to invaders, orchestrate acute response
- Found on surfaces of mast cells and basophils
allergy, how is it caused
- Antigens (normally harmless to people) perceived as threats
- Anti-allergen IgE triggers release of chemicals like histamine from mast cells
- Causes itching, swelling, (if lungs)
how is Anaphylaxis caused
○ Severe allergy
○ Excess histamine triggers smooth muscle contraction, interferes breathing when lung mucles contract, also weakens junctions between cells lining blood vessels
§ Causes them to leak
§ Fluid forced from circulation into tissues
§ Fluid has histamine, reaction spreads rapidly
○ EpiPens: Camp increases which increases circulation
Complement as part of adaptive immunity
- Antibodies made as part of the adaptive response activate complement through the classical pathway
- Requires additional proteins, C3 main player
Lectin-mediated pathway
- Similar to classical
- Produced by liver, binds sugars on bacterial cells
Allow complement proteins to bind and trigger formation of C3 convertase, then the pathway is the same as the classical
- Produced by liver, binds sugars on bacterial cells
Need 3 complement pathways because
- Patients with deficiencies in complement are vulnerable to blood-borne pathogens that shapeshift
○ They change antigens to elude immune system
○ New antigens not recognized by antibodies, not caught
Gut mucosal immunity and microbiome
- Gut immune system components
○ Epithelial barrier with T cells that have encountered antigens
○ Dendritic cells reach between epithelial cells to sample antigens from microbiota
○ Specialized cells called M cells sample antigens
Sampled antigens constantly presented to macrophages B and T cells in layer under epithelial cells
slgA
- Secreted into lumen of the gut
- Coats microbiota components considered to be treats
Prevents bound microbes from penetrating barrier
- Coats microbiota components considered to be treats
why are the positioning and response of TLRs is important
- There are TLRs on epithelial cell side facing the gut lumen, sees antigens
- Also on basal side of the layer (sees less antigens)
TLRs on basal side more reactive than ones on the luminal side
- Also on basal side of the layer (sees less antigens)
