Mucosal immunity & antibodies Flashcards
Fc dependent antibody functions
Opsonization, Sensitization for killing by NK cells, sensitization of mast cells, transport across epithelium, transport across placenta
Fc receptors are made of…
Binding chain for antibody, α-chain and signaling chain with ITAMs or ITIMS, γ-chain
α-chain of Fc receptor determines which…
…isotypes of antibody can be bound.
Diversity in response from the same antibody from different immune cells…
…are due to that different immune cells express different Fc receptors and some only in response to other stimuli.
FcγRI
On macrophages, activates phagocytosis upon binding antigen-bound IgG. Binds IgG3 best due to long hinge.
FcγRIII
On NK-cells. Binds IgG1 and IgG3, that is bound antigen on target cell. Binding causes NK-cell to kill target host cell.
FcεRI
On eosinophils and mast cells. Binds antigen-bound IgE. Causes eosinophil activation on a parasite. Mast cell is “armed” with empty receptor.
FcεRI mediated degranulation
FcεRI cross-linking causes release of histamine, heparin, trypase and TNFα from mast cells.
Type I allergy
IgE allergy; allergen induce IL-4 response, causes IgE production, IgE leads to “armed” mast cells, that are activated upon second exposure
Oral Immunotherapy
Very small amounts of allergens are ingested with pills. Treg should be activated to give a little tolerance
FcRn
Transports IgG across blod vessel by transcytosis
Transcytosis
Receptor-mediated transport of a molecule from one side of a cell to the other
Poly-Ig receptor
Transports dimeric IgA and IgM across mucosa by their J-chain.
Secretory IgA functions
To neutralise at mucosal surfaces and to bind antigens from the lamina probria and bring them with it during transcytosis
