part 10 Flashcards
how is a B cell activated
by antigen and helper T cell, which leads to antibody secretion by plasma cells.
what are the three outcomes of B cell activation
Neutralization: antibody prevents bacterial adherence
Opsonization:antibody promotes phagocytosis
Complement Activation: antibody activates complement, which enhances opsonization and lyses some bacteria.
what effector functions do antibodies heavily rely on
isotype switching
what is TD activation
require the activation of B cells by helper T cells that respond to the same antigen; this is called linked recognition.
what is the first signal in B cell
BCRs
what is the second signal in T cells
CD28 to bring in PI3K to secrete IL-2
what is the second signal in B cells
CD40 and IL-4.
This allows for cell proliferation, Ig class switching, and affinity maturation.
IL-5 and IL-6 are required in later steps.
what is TI activation
activate B cells in the absence of MHC class II-restricted T cell help.
what type of antigens activate B cells in TI
TI antigens are generally large polymeric molecules (such as polysaccharides) that have repetitive subunits capable of cross-linking mIg on the B cell surface
what are like the TLRs in signal 2
PRRs
what does CD19 do in B cells
bring in PI3K
similar to CD28 in T cells
what is CD21/CR2
CD21/CR2 recognizes complement proteins attached to the pathogen
This is similar to CD4/8 and CD28 interactions in T cells.
what happens when a pathogen is bound by the antibody receptor plus the coreceptors
activation increase by 10,000 times
what happens when the B cell is engaged by antibody:coreceptors, and is presented to T helper cell:CD40:IL-4, 5, 6
B cell proliferation
what can B cells differentiate into
resting memory cells or antibody-secreting plasma cells
what is linked recognition
T cells recognize one specific protein, while B cells recognize a different one.
However, they do recognize the same antigen; cognates.
what helps maintain self-tolerance
B cells can recognize self-peptides, but T cells can’t be activated through self-peptides due to not sufficient receptors
Dendritic cells link cognate T and B cells
what can B cell antibody receptors recognize
3D shapes linked to the pathogen (like a sugar)
what will antibodies recognize once the B cell breaks down antigen and is activated
secreted antibodie will recognize what macromolecule was recognized on the surface of the antigen
what is a hapten
a antigen that is too small to be detected/recognized by immune cells
how does the immune system respond to haptens
A carrier protein tricks the immune system into mounting a response
why are carrier proteins important irl
can be helpful for vaccines, but can cause allergic reactions (like to penicillin or antibodies)
what happens when a helper T cell binds to B cell and begins to synthesize IL-4 and CD40L
MTOC rearranges the cytoskeleton, most notably the Golgi apparatus
what is cell is the golgi rearranged
in the T helper cell
