T & B Cells and MHC Flashcards
Define HLA
Human Leukocyte Antigen - a gene complex responsible for encoding the MHC
Define MHC
Major Histocompatibility Complex - allows the acquired immune system to recognise foreign molecules
What do T cells derive from
Bone marrow stem cells
Where do T cell precursor cells arrive after leaving the bone marrow and how long do they spend here?
The thymus
7-21 days
What happens to the T cell precursor cells to facilitate their change into T cells
Differentiation & Proliferation
What percentage of thymocytes (lymphocytes within the thymus) die in the thymus?
Over 95%
What are CD4 & CD8 examples of?
Glycoproteins that are found on the surface of immune cells
Cell surface markers
What type of cell surface marker is dramatically affected in HIV?
CD4
What is the primary reason that T cells die before becoming useful?
Lack of ‘positive selection’ - i.e. the T cells don’t see the MHC so no need to respond to anything, so die
When do T cells become auto-reactive?
Negative selection, i.e. the T cells see the MHC too well
What must occur in order for a T cell to recognise and bind to an antigen?
MCH MUST BIND TO TcR
What is the actual function of the MHC?
To present the antigen for recognition
On what cells is MHC Class 1 expressed?
All cells apart from neural tissue & RBCs (lesser concs)
On what cells is MHC Class 2 expressed?
Limited to specialised antigen presenting cells & immune cells
By which cells is MCH Class 1 recognised by?
CD8 T cells
