Humoral Immunity Flashcards
humoral immunity components
- Th2 helper T-cells
- antigen-specific B-cell – plasma cells, memory cells
B-cell receptor complex
- activate B-cells to become plasma cells
- antigen-recognition molecules
- accessory intracellular-signaling molecules
3 signals required for B-cell activation
- antigen signal
- co-stimulatory signal
- cytokine signal
B-cells are activated by ____
direct antigen signal
B-cell activation results in ____
B-cell becoming plasma cell, class switch, proliferation, and antibody secretion
antibodies are also called _____
immunoglobulins
antibody general structure
- polypeptide chains
- antigen-binding fragment
- crystalline fragment
there are ____ classes of antibodies that all have different ____
5;
functions
4 structures of antibodies
- monomer
- dimer
- trimer
- pentamer
activated B-cells can change the ____; new ___ determined by ___
class of the antibody; class; cytokine signals and type/amount of antigen
in class switch, _____ change but ____ stays the same
constant regions of heavy chains (crystalline fragment);
antigen specificity
it is possible to activate B-cells independent of T-cells, if there is a _____; example?
very big antigen signal;
lipopolysaccharide
it is possible to activate B-cells independent of T-cells, and the result is ____ because _____
plasma cells that only produce IgM; will not get a class switch due to absence of cytokine signal and co-stimulatory signal
antibody functions: indirect
- complement activation
- opsonization
- ADCC (antibody dependent cell-mediated cytotoxicity)
antibody functions: direct
- neutralization
- agglutination
- precipitation
complement activation
classical pathway of complement pathway is dependent upon the presence of antibody-antigen complex to activate C1
opsonization
some cells have crystalline fragment receptors – these cells look for and will bind to the crystalline fragment on the antibodies and that will act as an opsonin and initiate phagocytosis of any bacteria they’re attached to
ADCC:
- used to ____
- activates ____
- requires ____
destroy large organisms, virus infected cells, and cancer cells;
NK cells, macrophages, or eosinophils;
prior antibody response
neutralization of bacterial toxins
- antibodies produced against a toxin to remove it from solution and prevent it from interacting with a cell
- ex: tetanus vaccine
neutralization of viruses
antibodies can directly interact with viruses and take them out of solution to prevent it from infecting a cell
agglutination
IgM can cross-connect to multiple bacteria at once which can allow our antibodies to cause a clumping of bacteria and hold them in place so our immune cells can come in to attack and destroy bacteria
precipitation
- if soluble antigens are being produced by bacteria, they can be directly attached by the antibodies and they can “pull them out of solution” (make them insoluble) so they accumulate
- precipitation prevents it from moving through the body and allows immune system to destroy and clear it out
- can also be useful in testing
IgM
- largest of the immunoglobulins
- pentamer stabilized by a J-chain
- first antibody produced during the primary response to an antigen
- synthesized during fetal life
IgG
- most abundant class
- transported across the placenta
- four classes: IgG1, IgG2, IgG3, IgG4
IgA
- IgA1 molecules: predominantly in blood
- IgA2 molecules: predominantly in secretions
- dimers anchored by J-chain and secretory piece
- secretory piece may protect IgAs against enzyme degradation from bacteria
secretory immune system
- lymphoid tissues throughout the body
- antibodies present in: tears, sweat, saliva, mucus, breast milk
- IgA is dominant Ig class
IgE
- least concentrated Ig class in circulation
- binds to surface of mast cells and basophils
- defender against parasites
- mediator of many common allergic responses
IgD
- low concentration in the blood
- primarily found on the surface of B lymphocytes
- function as one type of B-cell antigen receptor
memory B-cells
doesn’t get activated all the way to plasma cell; in “arrested development” waiting for signal to initiate remainder of differentiation to become plasma cell
memory T-cells
- effector activity declines with removal of antigen
- memory T-cells may remain for >20 years
fetal and neonatal immunity
- antibody function is deficient
- passive immunity provided by maternal antibody (maternal IgG across placenta, secretory IgA in breast milk)
aging and immune function
- decreased T-cell activity (thymus atrophy over lifespan)
- decrease in circulating memory B-cells
- decreased macrophage activity (increase in circulating antigen-antibody complexes)
- tolerance systems fail (increase in circulating auto-antibodies)
