Cluster of differentiation

Cluster of differentiation (CD) is a protocol used for the identification and investigation of cell surface molecules present on white blood cells initially but eventually on a wide variety of cell types. It is a vital part of the immune system and plays a significant role in cell signaling, cell adhesion, and cell differentiation.

History

The CD system was first established in the 1st International Workshop on Human Leucocyte Differentiation Antigens in 1982, with the aim to standardize the naming and description of different cell surface molecules. Since then, it has been expanded and updated in subsequent workshops.

Classification

CD molecules are classified based on their molecular structure, function, distribution, and the type of cell they are expressed on. They are numbered in the order of their discovery rather than their function or structure. As of 2021, over 400 CD molecules have been identified.

Function

CD molecules perform a wide range of functions. Some act as receptors or ligands in cell signaling, others are involved in cell adhesion, and some have roles in cellular immunity, apoptosis, or cell migration.

Clinical significance

CD molecules are often used as cell markers in immunophenotyping, allowing cells to be defined based on what molecules are present on their surface. This can be useful in diagnosing different types of lymphoma and leukemia, and can also be used to sort cells into different populations based on their surface characteristics.

See also

• Monoclonal antibodies
• Flow cytometry
• Immunology