c39 lec 6.5 and 7 Flashcards
(78 cards)
what is the main function of B cells
to produce antibodies
where are antibodies present
in the blood, lymph, and extracellular fluids
where they bind to extracellular bacteria and viral particles
also found at mucosal surfaces
how are B cells activated?
multiple surface B cell receptors bind to the same antigen and this causes B cell receptors (BCRs) to cluster together … this clustering and CROSS linking sending activation signals into the B cell
antigen interactions with IgM-BCRs on a B cell surface bring multiple BCRs close together
cross linking
this allows for signalling cascades to proceed and induce activation
describe the structure of a T cell receptor (TCR)
made up of 2 polypeptides, alpha chain and beta chain
have a variable and constant region
(V alpha and B beta, C alpha and C beta)
what type of pathogens are presented on MHC class I to mediate cell killing
intracellular pathogens
what type of pathogens are what professional antigen presenting cells uptake, process and present on MHC class II
extracellular pathogens
why are CD4 helper T cells called help cells? what help do they provide?
they produce cytokines, this helps macrophages degrade the pathogens that they uptake and furthermore they help B cells with the production of antibodies
proteins are degraded into peptides that can be loaded onto MHC molecules
antigen processing
pathogens proteins are broken down into peptides (in the cytosol) moved to the ER and then to plasma membrane to be present on MHC class ____
MHC class I
protein transports proteasome peptides to the ER for loading of MHC class I proteins
TAP: transporter associated with antigen processing
MHC class I is assembled where and then transported to where
ER to plasma membrane/cell membrane
where does peptide loading happen for MHC class I
in the ER
trims peptides to the right size for MHC class I antigen presentation
endoplasmic reticulum aminopeptidase (ERAP)
because peptides must be within a specific size range for MHC class I
- happens in the ER but it happens after the peptide is loaded
where does MHC class II get made
in the ER
how do we ensure that peptides that are supposed to bind to MHC class I don’t bind to MHC class II in the ER
CLIP: class II associated invariant chain peptide: MHC class II presentation is carefully regulated by multiple proteins including CLIP
- CLIP basically takes up MHC II binding pocket in the ER so peptides don’t bind
antigens are brought in through MHC II pathway in professional antigen presenting cells (pAPCs) but presented on MHC class I to activate CD8 T cells
cross-presentation : only applies to pAPCS
its when extracellular antigens are presented on MHC class I
white blood cells move from blood into tissues
diapedesis/extravasation
if T cells recognize class I in the thymus then is it
CD8 cytotoxic T cells
if T cells recognize class II in the thymus then it is
CD4 helper T cells
_______proteins are co-receptors to the TCR that also ensure that CD4 helper T cells bind to MHC class II and CD8 cytotoxic T cells bind to MHC class I
CD4 and CD8
what are the three signals that T cells require to be activated?
- TCR and CD4 and CD8 co-receptor recognize a specific peptide presented on MHC class II/I
- costimulatory receptor, CD28, binding to B7 on antigen presenting cell (APC) that is presenting antigen
- cytokines
- need all signals for the T cell to be activated
what is the T cell inhibitory co-receptor and what is the T cell activation co- receptor
activation: CD28
inhibitory/no activation: CTLA-4
once T cell gets first and second activating signal what happens
it starts to produce IL2
the IL2 goes into external environment and acts on the T cell that made it
