0502 - Lymphocyte Development II - EG Flashcards
What do T cells recognise?
antigenic peptides displayed on the surface of the body’s own cells.
What cells are antigen presenting cells?
dendritic cells, B cells, and macrophages.
What does HLA stand for? What are they?
Human leukocyte antigens. Products of MHC genes, both class I MHC and class II MHC.
What does MHC stand for?
Major histocompatibility complex, region of genes encoded on chromosome 6.
What do the HLA regions A, B, and C (ie HLA-A, HLA-B, and HLA-c) code for?
MHC class I
What do the HLA regions: HLA-DP, HLA-DQ, and HLA-DR, code for?
MHC class II
Where are MHC class I expressed? To what type of T cells do they present antigens?
On the surface of all nucleated cells. Present antigens to CD8+ T cells.
Where are MHC class II expressed? To what type of T cells do they present antigens?
On the surface of specialised antigen presenting cells, dentritic cells, macrophages, B cells. Present antigens to CD4+ T cells.
Where do T cells originally arise from?
Firstly derived from progenitors of the pluripotent haemopoietic stem cells of the bone marrow, then travel as undifferentiated lymphocytes to the thymus where they differentiate into T cells (various types).
List some of the phases/stages of T cell development
DN1 - immature thymocytes; DN2 - pro-T cell, expression of RAG-1 and RAG-2 for TCR beta chain D-J rearrangement; DN3 - pre-T cell, further beta chain V to DJ rearrangement; DN4 - proliferation by IL-2 signal; surrogate alpha chain (V-J) expressed and CD3. DP - CD4 and CD8 expression.Positive and negative selection stage. SP - expression of either CD4 or CD8.Mature T cell leaves thymus
What type of MHC does a CD4 T cell recognise?
MHC class II (dendritic cells, macrophages, B cells)
What type of MHC does a CD8 T cell recognise?
MHC class I (all nucleated cells)
What is positive selection?
Thymocyte development stage where T cells that are able to bind to a self-MHC will survive, and those that do not recognise a self-MHC die by apoptosis.
What is negative selection?
Thymocyte development stage where T cells that bind strongly to a self-peptide-self-MHC will die by apoptosis to prevent auto-reactivity.
What cells facilitate the negative selection stage of T cell development?
Thymic medullary epithelial cells, which express a nuclear protein autoimmune regulator (AIRE) to induce the expression of tissue specific genes in the thymus to make a range of tissue specific peptides available for presentation to developing T cells.
