Does CTLA-4 compete with CD28?

Immunological Tolerance CTLA-4 competes with CD28 for B7 binding and interacts with clathrin adaptor proteins and tyrosine phosphatases via its cytoplasmic domain to control cell trafficking and set the activation threshold in T cells. CTLA-4 is essential for regulatory T cell function.

What is the function of CTLA-4?

A protein found on T cells (a type of immune cell) that helps keep the body’s immune responses in check. When CTLA-4 is bound to another protein called B7, it helps keep T cells from killing other cells, including cancer cells.

What does CTLA-4 interact with?

(A) In health, regulatory T cells express CTLA-4, which binds CD80 and CD86 expressed on antigen presenting cells (APCs). CTLA-4 binds to CD80 and CD86 with higher affinity and avidity than does CD28, preventing Tcon stimulation through CD80/CD86 interaction with CD28.

What is CTLA-4 expressed?

CTLA-4 is a molecule expressed on T cells after activation and strongly binds to co-stimulatory molecules on antigen-presenting cells that prevent binding of these molecules needed for T-cell activation. The CTLA-4 molecule acts as a halting mechanism, decreasing the function of T cells.

What type of receptor is CTLA-4?

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) (CD152) and CD28 are homologous receptors expressed by both CD4+ and CD8+ T cells, which mediate opposing functions in T-cell activation. Both receptors share a pair of ligands expressed on the surface of antigen-presenting cells (APCs).

What is the mechanism of action of CTLA-4 in T-cell activation?

Is CD28 the T cell receptor?

CD28 is the only B7 receptor constitutively expressed on naive T cells. Association of the TCR of a naive T cell with MHC:antigen complex without CD28:B7 interaction results in a T cell that is anergic.

How does CTLA-4 inhibit T cell activation?

After T-cell activation, CTLA-4 is stored in the intracellular vesicles, and recruited to the immunological synapse formed between T cells and APCs, and inhibits further activation of T cells by blocking signals initiated by T-cell receptors and CD28.

What is CD28 expressed on?

In humans, CD28 is expressed on approximately 80% of CD4+ T cells and 50% of CD8+ T cells and has been detected on plasma cells, neutrophils, and eosinophils.