CD4-positive, CD25-positive, alpha-beta regulatory T cell differentiation

Definition

Target type: biologicalprocess

The process in which a precursor cell type acquires the specialized features of a CD4-positive, CD25-positive, alpha-beta regulatory T cell. [GOC:add, PMID:15207821]

CD4-positive, CD25-positive, alpha-beta regulatory T cells (Tregs) are a specialized subset of T lymphocytes that play a critical role in maintaining immune homeostasis and preventing autoimmunity. Their differentiation is a complex process involving multiple signaling pathways and transcription factors. Here's a detailed breakdown:

1. **Development in the Thymus:** Tregs originate in the thymus, where they undergo a unique developmental program. During thymic development, immature T cells encounter self-antigens presented by thymic epithelial cells. This interaction can lead to two distinct outcomes:
* **Positive selection:** T cells recognizing self-antigens with low affinity undergo positive selection, ensuring that they can recognize self-MHC molecules but not attack self-tissues.
* **Negative selection:** T cells recognizing self-antigens with high affinity undergo negative selection, eliminating cells that could potentially cause autoimmunity.

2. **Treg Specification:** A subset of thymocytes that undergo positive selection encounter self-antigens presented by thymic epithelial cells in the context of a specific co-stimulatory molecule, CTLA4. This interaction, along with the cytokine TGF-β, triggers the expression of the transcription factor Foxp3. Foxp3 is the master regulator of Treg development and function, and its expression marks the commitment of these cells to the Treg lineage.

3. **Peripheral Induction:** While the majority of Tregs develop in the thymus, a significant portion can be generated in the periphery from naive CD4+ T cells, a process known as peripheral Treg induction. This induction requires specific conditions, including:
* **Exposure to self-antigens:** Naive CD4+ T cells encounter self-antigens in the periphery.
* **Presence of TGF-β:** TGF-β acts as a crucial cytokine for Treg induction, triggering Foxp3 expression and promoting the differentiation of naive CD4+ T cells into induced Tregs.
* **Other factors:** Additional factors, like retinoic acid, IL-2, and IL-10, can also influence peripheral Treg induction.

4. **Treg Function:** Mature Tregs exhibit several key characteristics:
* **Suppression of Immune Responses:** Tregs suppress the activation and proliferation of other immune cells, such as conventional T cells, preventing excessive immune responses and autoimmunity.
* **Immunosuppressive Mechanisms:** Tregs use various mechanisms to suppress immune responses:
* **Cytokine Production:** They produce immunosuppressive cytokines like IL-10 and TGF-β, which dampen the activity of other immune cells.
* **Depletion of T cell co-stimulatory molecules:** Tregs express CTLA4, a molecule that competes with CD28 for binding to CD80/CD86 on antigen-presenting cells (APCs), reducing T cell activation.
* **Metabolic Modulation:** Tregs can deplete the local environment of nutrients like glucose, hindering the metabolic requirements of other T cells.
* **Direct cell-cell contact:** Tregs can directly interact with other immune cells, inducing their apoptosis or suppressing their function.

5. **Treg Stability and Plasticity:** Tregs are generally considered stable, maintaining their suppressive function over time. However, they can exhibit some degree of plasticity, under certain conditions, differentiating into other T cell subsets like Th17 cells.

6. **Importance in Immune Homeostasis:** Tregs play a critical role in maintaining immune tolerance by preventing excessive immune responses against self-antigens and controlling immune responses against commensal bacteria and other environmental antigens. Dysregulation of Treg function can lead to autoimmune diseases and other immune-related disorders.'
"

Proteins (2)

Compounds (14)