CDs (clusters of differentiation)

Clusters of Differentiation (CDs) constitute an internationally standardized nomenclature system used to identify cell surface molecules, mainly on immune system cells. Each CD corresponds to a specific protein or protein complex with defined functions, enabling the distinction between different cell types as well as their states of differentiation and activation.

In flow cytometry, CD markers are central elements for the phenotypic and functional characterization of cellular populations. The combination of multiple CDs allows the precise identification of cellular subpopulations, such as CD4⁺ and CD8⁺ T lymphocytes, CD19⁺/CD20⁺ B cells, CD14⁺ monocytes, among others.

Beyond defining cell lineage, many CDs function as markers of cellular activity, reflecting states of activation, exhaustion, migration, and inflammatory responses. Accordingly, CD-based flow cytometry is widely applied in basic and translational research, immunophenotypic diagnosis, monitoring of immune-mediated diseases, and the development of targeted therapies.

The standardization of CDs is essential for experimental reproducibility and for the comparison of results across different studies and laboratories, consolidating flow cytometry as one of the main tools of modern immunology.