Foundations in Immunology 3 Flashcards
Where are T cells produced and matured?
- Produced in bone marrow
- Matured in thymus
What are T cells responsible for?
Cell mediates immunity and assisting B cells
What is the cell surface receptor on a T cell?
T cell receptor which only recognises Ab when bound to MHC
What T cells stimulate B cells to produce Ab?
Helper and CD4
What are cytotoxic T cells?
CD8
How do B cells recognise Ag?
Recognise free organic antigen via BCR (surface IgM)
How do T cells recognise Ag?
- Ag epitopes may be hidden from Ab
- T cells need to be shown protein antigen in association with MHC
- Because Ag in small peptides all epitopes available to TCR
In what way must T cells be restricted?
- Must learn not to recognise self antigens
- Must also be restrictd to recognise Ag in association with our own MHC
What is positive selection?
-Thymocytes enter the thymus and migrate to cortex and proliferate.
They begin to express CD4, CD8 and TCR
-They are presented with self MHC on epithelial cells.
-Those that recognise it live, the rest undergo apoptosis
What is negative selection?
T cells which recognise MHC plus self peptide on dendritic cells undergo apoptosis
What is the final result of positive and negative selection?
T cells with receptors which will not react to self antigen presented by MHC on thymic dendritic cells but will react to MHC-peptide complexes on thymic epithelial cells.
What is the purpose of Class 1 MHC?
- Found on virtually all nucleated cells
- Presents virally induced peptides to CD8 T cells and trigger cytotoxic response
What is the purpose of Class 2 MHC?
- Found only on Professional Antigen Presenting cells
- Presents exogenously produced Ag to CD4 T cells and activate macrophages and B cells
What are T helper cells essential in?
- B cell Ab class switching
- Activation and growth of Tc
What are T helper cells?
Cells which activate and direct other immune cells.
-they cannot kill infected cells or pathogens
