The regulatory t cells (tregs

1. The regulatory T cells ( Tregs Eman youssif

2. formerly known as suppressor T cells, are a subpopulation of T cells which modulate the immune system, maintain tolerance to self-antigens, and abrogate autoimmune disease. Mouse models have suggested that modulation of Tregs can treat autoimmune disease and cancer, and facilitate organ transplantation .

3. T regulatory cells are a component of the immune system that suppress immune responses of other cells. This is an important "self-check" built into the immune system to prevent excessive reactions. Regulatory T cells come in many forms with the most well-understood being those that express CD4, CD25, and Foxp3 (CD4+CD25+ regulatory T cells, or " Tregs ").[1] These cells are involved in shutting down immune responses after they have successfully eliminated invading organisms, and also in preventing autoimmunity

4. CD4+ Foxp3+ regulatory T cells have been called "naturally-occurring" regulatory T cells to distinguish them from "suppressor" T cell populations that are generated in vitro. Additional suppressor T cell populations include Tr1, Th3, CD8+CD28-, and Qa-1 restricted T cells. The contribution of these populations to self-tolerance and immune homeostasis is less well defined. FOXP3 can be used as a good marker for mouse CD4+CD25+ T cells, although recent studies have also shown evidence for FOXP3 expression in CD4+CD25- T cells. In humans, FoxP3 is also expressed by recently activated conventional T-cells and thus does not specifically identify human T- reg .[citation needed] An additional regulatory T cell subset, induced regulatory T cells, are also needed for tolerance and suppression

5. All T cells come from progenitor cells from the bone marrow, which become committed to their lineage in the thymus. All T cells begin as CD4-CD8-TCR- cells at the DN (double-negative) stage, where an individual cell will rearrange its T cell receptor genes to form a unique, functional molecule, which they, in turn, test against cells in the thymic cortex for a minimal level of interaction with self-MHC. If they receive these signals, they proliferate and express both CD4 and CD8, becoming double-positive cells. The selection of Tregs occurs on radio-resistant haemopoietically -derived MHC class II-expressing cells in the medulla or Hassal’s corpuscles in the thymus. At the DP (double-positive) stage, they are selected by their interaction with the cells within the thymus, begin the transcription of Foxp3, and become Treg cells, although they may not begin to express Foxp3 until the single-positive stage, at which point they are functional Tregs . Treg do not have the limited TCR expression of NKT or γδ T cells; Treg have a larger TCR diversity than effector T cells, biased towards self-peptides.