Antigen Capture and Presentation to Lymphocytes Flashcards
TCR and MHC interaction
TCR/ T cells require MHC (MHC dependent)
peptide Ag at the MHC will interact with the variable region of the TCR
anchor residues of the peptide will anchor the Ag in the MHC pockets
Recognition of antigens by antibodies
can be mem bound or soluble
broaber specifity than TCR: can recognize more than just peptides
Migration of T lymphocytes
naive lymphocytes present in the LN, sample Ag
may encounter Ag and become active as an effector cell (Tc or Th), migrate to site
APCs
macrophages
dendritic cells
b cells
dendritic cell role
macrophage APC role
b cells APC role
Function of cytotoxic T cells (CTLs)
Role of Dendritic cells in antigen capture and presentation/ other important APCs?
what molecules does the DC use to recognize Ag?
found at skin, lungs, and GI: will capture Ag and migrate to peripheral LN or spleen
capable of recognizing the Ag via TLR or lecithin
once Ag is captured, cells lose adhesiveness for tissue and migrate and there is an increased expression of MHC and costimulators in the cell surface
will then interact with naive t cells to stimulate a t cell response
Macrophages and B lymphocytes are also important APCs
Costimulators are important for?
antigen presentation by dendritic cells to activate naïve T cells.
MHC
on APCs, will display Ag to TCR
MHC genetics
complex genes, class I and II loci that are highly polymorphic
class I MHC polymorphic regions peptide-binding cleft size what binds TC coreceptor which t cells respond to these?
Polymorphic regions: a1 and a2
Peptide-binding cleft for peptides 8-9 aa long
a3 binds CD8 T-cell co-receptor
CD8+ T cells can only respond to antigen presented
by MHC class I molecules
class II MHC polymorphic regions peptide-binding cleft size what binds TC coreceptor which t cells respond to these?
Polymorphic regions: a1 and b1
a2 and b2 bind CD4 T-cell co-receptor
Peptide-binding cleft for peptides 10-30 aa long
CD4+ T cells can only respond to antigens presented by MHC class II molecules
class II MHC on what cells
APCs
class I MHC on what cells
all nucleated cells
expression pattern of MHC alleles
codominant
significance of polymorphic MHC genes
many alleles in population
different people can present and respond to different microbial antigens
codominant expression of MHC significance
increases the number of possible MHC molecules
broad specificity of MHC
many peptides can bind the same MHC
how many peptides can each MHC molecule display at one time? why?
only one, each t cell responds to only one peptide at a time
MHC molecules bind only?
peptides
when are the peptides of MHC molecules acquired?
during intracellular assembly, I and II can display Ag/peptides from different intracellular compartments
stable surface expression of MHC requires?
a peptide to be bound
off rate of MHC
very slow, displays peptide long enough for T cell recognition
CD8+ Cytotoxic T cells (CTLs) recognize?
endogenous (cytosolic) antigen presented by MHC class I molecules on an infected cell
endogenous (cytosolic) antigen presentation mechanism?
CD4+ Helper T cells recognize?
exogenous antigen presented by MHC class II molecules on a professional antigen presenting cell (APC)
exogenous antigen presentation mechanism
cross-presentation
Class I MHC-restricted cross-presentation of microbial antigens from infected cells by dendritic cells
class II MHC pathway: Ag presentation to Th possible ways
two ways possible
microbe uptake by macrophage, present in endosome> use of class II to present Ag to CD4= cytokines to activate macrophage and kill microbe
Ag specific b cells bind extracellular Ag, present to Th via MHC II=cytokine production causing b cell to produce secreted Ab
class I MHC pathway: presentation to Tc
cytosolic Ag> Ag peptide associated with MHC I and presented to CD8 which then activates killing function and kills infected cell
