Cluster of Differentiation 80 (also CD80 and B7-1) is a protein found on activated B cell
B cell
B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...

s and monocyte
Monocytes are a type of white blood cell and are part of the innate immune system of vertebrates including all mammals , birds, reptiles, and fish. Monocytes play multiple roles in immune function...

s that provides a costimulatory signal necessary for T cell
T cell
T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...

 activation and survival. It is the ligand
Ligand (biochemistry)
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is a signal triggering molecule, binding to a site on a target protein.The binding occurs by intermolecular forces, such as ionic bonds, hydrogen...

 for two different proteins on the T cell surface: CD28
CD28 is one of the molecules expressed on T cells that provide co-stimulatory signals, which are required for T cell activation. CD28 is the receptor for CD80 and CD86 . When activated by Toll-like receptor ligands, the CD80 expression is upregulated in antigen presenting cells...

 (for autoregulation and intercellular association) and CTLA-4
CTLA4 also known as CD152 is a protein that plays an important regulatory role in the immune system...

 (for attenuation of regulation and cellular disassociation). CD80 works in tandem with CD86
Cluster of Differentiation 86 is a protein expressed on antigen-presenting cells that provides costimulatory signals necessary for T cell activation and survival...

to prime T cells.

Further reading

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