Antigen Processing & Presenting Flashcards
Qualifications to be a professional Ag-presenting cell
- Express MHC II
- Present Ag to CD4 T-cells
- Activate CD4 T-cells
Professional Ag-Presenting Cells
ONLY use MHC II
Types of Professional Ag-Presenting Cells
Myeloid Dendritic Cells (DCs)
Macrophages
B-cells
Types of Dendritic Cells
- Myeloid
2. Follicular
Function of Myeloid Dendritic Cells
capture Ags & present to CD4 cells
Location of Myeloid Dendritic Cells
diffuse lymphoid, connective tissue, epithelia
Function of Follicular Dendritic Cells
retain Ags for B cells
T-cell & dendritic cell interactions
T-cells sample the Ags DCs present to see if the DCs have something the T-cells can respond to.
they are NOT just idly sitting around waiting for things to “bump” into them.
Methods of Getting Exogenous Antigens
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis
After the Ag has been internalized by an Ag-specific B-cell and fragmented, it…
is presented on the membrane at a HIGH density.
Ag pathway with M cells
M cells endocytose and phagocytose Ag and transport it across cell for release at basal surface where Ag binds to DCs that then go activate T-cells
Antigenic peptide (T cell epitope)
only one side of the peptide chain is presented to the T-cell
TCR contacts…
Ag and MHC molecule.
Why is MHC an important determinant of transplant tissue success?
Each MHC molecule has different conformities (b/c of polymorphism) than the resident T-cells normally see, SO the T-cells view them as Ags.
“Non-professional” APCs…
can be induced to express MHC II by exposure to cytokines like IFN-gamma
Myeloid Dendritic Cells Ag uptake (exogenous Ags)
phagocytosis
pinocytosis
receptor-mediated endocytosis
Macrophages present Ags primarily to…
effector CD4 and CD8
memory CD4 and CD8
B Lymphocyte Ag uptake (exogenous Ag)
receptor-mediated endocytosis
Myeloid Dendritic Cells present Ag primarily to…
naive CD4 & CD8
effector CD4 & CD8
memory CD4 & CD8
Macrophage Antigen uptake (exogenous Ag)
phagocytosis
pinocytosis
receptor-mediated endocytosis
B Lymphocytes present Ags primarily to…
effector CD4 Tfh
memory CD4 Tfh
Activated Myeloid DCs…
Langerhans cells (DCs) uptake Ag in skin & leave it to enter lymphatic system. The mature Langerhans enters lymph node & transfers Ags to resident DCs. B7-positive DCs stimulate naive T-cells
Dendritic Cells Activated by…
PAMPs, DAMPs, IL-1, TNF-a, IFN-a, IFN-beta
Activated DCs actions =
- migrate to diffuse lymphoid tissues
- present Ag to T-cells (signal 1)
- deliver signal 2 to T-cells
- deliver signal 3 to T-cells
