B cells Flashcards
List the effector functions of B cell antibodies
Neutralization of microbes and toxins, opsonization and phagocytosis of microbes, antibody-dependent cellular cytotoxicity, complement activation, inflammation, and lysis of microbes
What are the functions of the Fc receptor?
Deliver antibody to inaccessible anatomical sites and link bound antigen to molecules/cells that effect destruction
What region of the antibody does complement And Fc receptors bind to?
Fc
T/F: Antigen-bound antibodies can bind to Fc receptors in order to act as opsonins or to activate cells
True
Describe the affinity for Ig, cell distribution, and function of the Fc receptor Fc-gamma-RI (CD64)
High affinity and can bind IgG1, IgG3, and monomeric IgG; found on macrophages, neutrophils, and eosinophils; function is phagocytosis and activation of phagocytes
Describe the affinity for Ig, cell distribution, and function of the Fc receptor Fc-gamma-RIIA (CD32)
Low affinity for Ig; found on macrophages, neutrophils, eosinophils, and platelets; functions in phagocytosis and cell activation (inefficient)
Describe the affinity for Ig, cell distribution, and function of the Fc receptor Fc-gamma-RIIB (CD32)
Low affinity for Ig; found on lymphocytes, DCs, mast cells, neutrophils, and macrophages; function is feedback inhibition of B cells and attenuation of inflammation
Describe the affinity for Ig, cell distribution, and function of the Fc receptor Fc-gamma-RIIIA (CD16)
Low affinity for Ig; found on NK cells; function is antibody-dependent cellular cytotoxicity (ADCC)
Describe the affinity for Ig, cell distribution, and function of the Fc receptor Fc-epsilon-RI
High affinity for monomeric IgE; found on mast cells, basophils, and eosinophils; function is activation (degranulation) of mast cells and basophils
What are some effects of antibody binding to antigens or toxins as it relates to neutralization?
Blocks penetration of microbes through epithelial barriers, blocks binding of microbe and infection of cells, and blocks binding of toxins to cellular receptors and thus, the associated pathological effects
Explain the process of opsonization and phagocytosis
Microbe is floating around and gets opsonized (bound) by antibodies; the opsonized microbe (immune complex) binds to its Fc receptor; the Fc receptor sends signals that activate the phagocyte; this results in phagocytosis of the immune complex and subsequent killing of the ingested microbe
What is the function of CR1 on erythrocytes?
Binds circulating immune complexes with attached C3b and C4b and transports the complexes to the liver and spleen; organ resident phagocytes remove the immune complexes from the erythrocyte surface and the erythrocytes continue to circulate
Describe the process of NK killing of a cell infected with a virus
Virus infects a cell and surface antigens are placed on the surface of the infected cell; antibodies bind to the antigens on the cell surface, tagging it as “infected”; NKs with Fc receptors for that antibody bind to the Fc region of the antibody and kill the antibody-coated cell
What is the function of intravenous Ig (IVIG)?
For rapid protection after exposure to a disease; also used in autoimmune or inflammatory diseases by engaging the inhibitory FcR on B cells and (maybe DCs?) and suppresses the immune response
What are the natural antibodies and who produces them? What is their function?
IgM mainly, but some IgG; produced by B-1 and marginal zone B cells; specific for bacteria in the area and cross react with blood alloantigens
What do IgA and IgM have in common?
Both have J chains
Explain the exchange of IgG between a mother and a fetus
IgG can leave the circulation and enter extracellular spaces within tissues via transcytosis via FcRn (natal FcR); this transports IgG from the maternal circulation across the placental barrier as well as the transfer of maternal IgG across the intestine; FcRn takes bound IgG and recycles it to the cell surface and releases it at neutral pH, returning the IgG to the circulation
Where is the FcRn found?
Surface of endothelial cells, macrophages, and other cell types
What antibodies are produced at the time of birth and what antibodies are produced 6-12 months post-birth?
IgM and then IgG and IgA come later
Define immunization
Antigenic stimulus that elicits a specific adaptive immune response(s) that can be recalled during subsequent infections