B cells and antibodies block B Flashcards
what turns the B cell on ?
cytokines
is the antibody produced the same specificity or different to the antigen ?
same specificity
what is the BCR structure ?
a surface bound version of Ig.
when does the b cell mature and what happens next ?
when it expresses the functional BCR , matures from the bone marrow and enters periphery where it migrates via lymph nodes.
what does the recognition of the antigen by the BCR lead to ?
activation of B cell and internalisation of antigen. Once internalised the antigen is broken down into peptides. These peptides are then loaded into MHC-II within the B cell and presented to antigen-specific CD4+ T cells. If the T cell also recognises the antigen then it will provide ‘help’ to the B cell (cytokines, co-stimulation). This allows the B cell to fully activate and secrete antibodies.
what process allows the antigen to be internalised ?
receptor mediated endocytosis
what does the CD40 do ?
provide help to the CD4+ helper T cells.
how do T cells influence antibody production ?
by secreting cytokines which induces proliferation of the B cell as well as differentiation.
if the antibody is chopped up , would the antigen recognise the epitope ?
no
what mechanism allows the immunoglobin molecule to have flexibility and allows them to bind to multiple antigens ?
hinge region
what’s the 3 mechanisms of antibodies ?
neutralisation
opsonisation
complement
where does the antigen bind ?
the Fc region of the antibody
describe neitralisation
mechanism in which the antibody produced from the B cells will bind to the antigens on the viruses surface which results in it no longer being able to bind to the host cell and can therefore no longer take over the host cell to cause further damage.
describe opsonisation ?
also involves the antibodies binding to the antigens on the viruses surface , however it does not block the viruses from binding to the host cell , instead it labels the pathogen so it Is recognised by a phagocytic cell so that the pathogen can be degraded using phagocytosis
describe complement ?
antibodies work together with the proteins involved in the complement system. When they bind together and bind onto a foreign cell this causes the membrane of the pathogen cell to swell up and burst.
what antibodies result in neutralisation ?
IgG and IgA
what type of molecule is IgM ?
a pentameric molecule.
what do the IgM bind to ?
C1q
the IgG can also bind to bacteria through their antigens , but how molecules are required to bind to C1Q ?
2
what part of the phagocyte do the antibodies bind to ?
the Fc receptor
when the C3b binds to Cr1 and the antibody binds to the Fc what does this result in ?
the bacteria being phagocytosed
when the membrane encloses in the macrophage aound the bacteria what forms ?
a phagosome
when the lysosome binds to the lysosome what forms ?
a phagolysosome
how is IgA transported ?
in the mucus , gut and milk.
what is IgG3 antibody associated with ?
allergies
why are different cells activated by different antibodies?
as the cells contain different Fc receptors
what receptor does mast cells express and what does it bind too ?
FceR1 , binds to IgE
when IgE binds to the antigen and cross links FceR1 what does this result in ?
degranulation of mast cells which causes anaphlyaxis
what is IgG and IgM classes associated with ?
bacteria and viruses
IgA is a dimer , what is it released into ?
mucous membranes.
does IgA play a role in locally or not locally defending the body from pathogens ?
locally
what is IgE involved in ?
allergic responses
