lecture 36 Flashcards
(18 cards)
what are B cells?
- lymphocytes that develop in the bone marrow
- Express unique antigen receptors
- Plasma cells are activated B cells that secrete antibody
- memory B cells provide ‘memory’
where do B cells originate and mature?
bone marrow
label the B cell receptor parts
what is a B cell receptor
- covers B cell
- mainly IgM and Igd antibodies
- binds antigen and activates the
B cell - membrane anchored via a
transmembrane domain
what are the functions of antibody?
- neutralisation
- opsonisation (make tasty for phagocytes)
- complement activation
what do antibodies bind to?
native antigen
what is native antigen?
antigen does not have to be
processed to peptide (or
in context of MHC).
what is the antigen binding site called?
epitope
where is IgG found and what is its function?
- most abundant in blood
- Opsonises/Neutralises
- crosses placenta for passive immunity
- targets virus and placenta
where is IgA found and what is its function?
- Present in secretions such
as tears, saliva, mucus, and
breast milk, monomeric form in blood - Defence of mucous membranes, esp. gut
- passive immunity via breast milk
- targets virus and bacteria
where is IgM found and what is its function?
- First Ig class produced after
initial exposure to antigen. - Expressed on naïve B cells
- activates complement
- Targets extracellular
bacteria - acts as antigen receptor
where is IgE found and what is its function?
- Present in blood at low concentrations
- Immunity to multicellular parasites
- Allergic reactions
- activates mast cells
where is IgD found and what is its function?
- Expressed on naïve B cells
- Together with IgM, acts as antigen receptor
- specific function unknown
Stimulation of B cells by antigen + T cell forms…
plasma and memory cells
what are memory cells
- persist for years in blood and lymphatic tissue
- Express antibody as BCR, but do not secrete antibody
- Respond rapidly to antigen encounter and become plasma cells
what are the features of the primary immune response?
- 7-14 days to eliminate pathogen
- Relatively low amount of antibody produced – mainly IgM.
what are the features of the secondary immune response?
- basis of vaccination
- relies on memory B cells
- 2-3 days
- sufficient antibody is produced to eliminate pathogen
- mainly IgG, with additional class switching to IgA and IgE
how is antibody produced?
- APC phagocytoses antigen
- MHC-II peptide complex interacts with TCR on T helper cell
- releases cytokines to activate B cell
- B cell receptor binds to native antigen
- plasma cell releases antibody
