Humoral Immunity Part 2 Flashcards
How long does a primary immune response take?
7-10 days
Describe the secondary immune response.
Takes 3-5 days to peak. Stronger and faster than primary immune response
Compare cell activation in primary vs secondary immune response.
Primary response activates on naive b cells. Secondary activates both memory and naive b cells.
How is the humoral immunity controlled?
Immune complexes binds to b cell at Fcy receptor on CM. This leads to cross-linking of membrane bound Ig and FcyR and removes the phosphate from ITM (signaling membrane protein).
What can antibodies do?
Opsonize, neutralize, Antibody-dependent cellular cytotoxicity. Activate complement
Describe status of membrane bound antibodies vs secreted ones.
All membrane-bound antibodies are monomers. When secreted they become polymers. They polymerize when a J chain joins.
- IgA can form mono/di/trimers
- IgM forms a pentamer.
- Secreted IgG and IgE remain monomers
- IgD is never secreted.
What is IgAs main function?
Mucosal immunity; Found in mucus, tears and milk
What is IgDs main function?
Activates naive B cells
What is IgEs main function?
Mast cell activation; Defends against worms
What is IgGs main function?
Opsonization, Cā activation, etc
What is IgMs main function?
Activates naive B cells, Cā activation.
What can all antibodies do?
Neutralize
Which cells can bind IgG?
Professional APCs, Eosinophils, Nk cells, and B cells all have FcyR.
Which cells can bind IgE?
Eosinophils, Mast cells, and Basophils all have FceR
Discuss Antibody-Dependent Cellular Cytotoxicity.
CD16 on Nk cells binds to the Fc region of IgG. Cross linking activates the NK cell to induce exocytosis of granules.
What does the basal side of epithelial cells in the GI, respiratory tracts, tear ducts and mammary glands have?
They all have poly Ig receptor; Binds to the J chain and activates transcytosis. On the apical side, an enzyme cleaves the poly Ig receptor releasing the secretory component. This increases the half-life of IgA and IgM.
Why does IgG have the longest half-life in serum?
FcRn can be found on placenta, endothelial cells and phagocytic cells. Recycles the antibody.
Discuss passive immunity
Fetal endothelial cells express FcRn on the basal side, exposed to maternal blood in the placenta. The FcRn-maternal IgG is transcytosed across into fetal blood vessels.
