Lecture 4.2 - Adaptive Immunity Flashcards
Name the 4 professional APCs
Dendritic cells
Langerhan’s cells
Macrophages
B cells
Where might you find dendritic cells?
Lymph nodes, mucous membranes and blood
Where are Langerhan’s cells found?
The skin
Explain how macrophages aid themselves by acting as APCs
By acting as APCs, they activate T cells. These in turn release cytokines which then aid the macrophages with phagocytosis
Explain how B cells aid themselves by acting as APCs
By acting as APCs, they activate T cells which in turn allow the B cells to undergo isotype switching
What are the 3 important features of professional APCs?
Strategic location
Able to capture pathogens via phagocytosis
Diverse PRRs so they recognise wide variety of PAMPs
Where are class I MHC molecules present?
On the surface of all nucleated cells
Briefly outline the mechanism by which class I MHC molecules present intracellular antigens
- Cytosolic proteins cleaved by proteasome
- Peptide fragments to ER where newly made MHC molecules are waiting
- If MHC and peptide match, forms complex
- Migrates to cell surface and presented to CD8+ cells
Where are MHC class II molecules found?
On the surface of professional APCs only - i.e. dendritic cells, macrophages and B cells
Briefly outline the mechanism by which class II MHC molecules present antigens
- Exogenous antigen phagocytosed and broken into fragments in endosome
- Endosome fuses with vesicle which has new MHC molecules on surface
- Peptide and MHC form complex –> migrates to cell surface and presented to CD4+
Explain why some patients appear to be able to control viral replication over a long period of time
Most likely have MHC molecules which present peptides key to viral survival, and hence cannot be mutated. Therefore their structure remains constant and T cells continue to recognise them.
Where are T cells made?
The bone marrow
What happens to T cells in the thymus?
They mature
What is a T cell receptor?
The receptor on a T cell which recognises antigenic peptides presented by APCs
What is a “naive” T cell?
A T cell which has not yet come into contact with any microbes
