T and B cell development - Hudig Flashcards
Name the primary lymphoid organs.
Bone marrow and thymus.
Where are B and T cells produced?
They are both produced in the bone marrow and then Pre-T cells migrate to the thymus to mature.
Where are NK cells produced?
In the bone marrow.
From what cell type do the lymphocytes originate from?
Pluripotent hematopoietic stem cells in the bone marrow.
What is central tolerance for B cells?
In the bone marrow, if an immature B cell reacts to self antigens it will die.
Describe T cell development.
- pre- T cells leave the bone marrow and travel by blood to the thymus. They lack CD3, CD4 and CD8 at this point.
- In the thymus they express CD25 so that they can respond to IL-2 and divide. They then express CD3, and both CD4 and CD8 together.
- T cells get their TCR’s.
- T cells are positively selected if they can bind weakly to self MHC proteins.
- T cells are negatively selected for binding too strongly to MHC alone or too strongly to MHC plus self peptide.
What happens to T cells with TCR’s that fail to bind to self MCH?
They die via apoptosis.
What is AIRE?
AIRE - autoimmune regulator is a protein in thymic medullary epithelial cells that induces expression of organ-specific proteins in the thymus to support the deletion of self-reacting T cells.
Are B an T cells produced throughout life?
Yes, but T cell production declines because the thymus starts to regress at puberty - so the ability to make naive T cells decreases with age.
Where does central tolerance take place?
In the primary lymphoid organs.
Where does peripheral tolerance take place?
In circulation. If they see self antigens but fail to get signal 2 then they die or become anergic.
What is a major difference between B and T cell tolerance?
B cell tolerance is easier to ‘break’ - since their is no AIRE protein in the bone marrow B cells have more potential for self-reactivity.
