Project Details NPU codes for characterizing subpopulations of the hematopoietic lineage, described from their Clusters of Differentiation (CD) markers

Project No.:
Start Date:
17 January 2022
End Date:


Several types of B- and T-lymphocyte subpopulations exist, which all have their unique role in the immune system, as well as in disease. Interpretation of lymphocyte subpopulation data for clinical practice requires the establishment of laboratory codes that are well-defined and precise with respect to which population that is detected. In this regard, detection of the Clusters of Differentiation (CD) markers present on the lymphocyte cell surface, is the only consistent method to differentiate between lymphocyte subpopulations. The objective of this project is therefore to create NPU codes for lymphocyte subpopulations, based on the use of the CD nomenclature.

(link to SC-NPU)


Numerous diseases are associated with alterations in peripheral blood lymphocyte subpopulations, including primary, secondary, and congenital immunodeficiency’s, autoimmune diseases, infections and cancer. Identification of lymphocyte subpopulations is necessary in these clinical conditions to establish diagnosis and as a criterion for disease progression and treatment optimization.

Prior to antigen stimulation, B- and T-lymphocytes appear morphologically similar. Therefore, no consistent method to differentiate functionally unique lymphocyte populations was present before the development of monoclonal antibodies specific to Clusters of Differentiation (CD) markers present on the lymphocyte cell surface. Today, more than 350 different CD antigens have been discovered, which identify the cell type populations and the stage of differentiation.

Currently, the NPU codes for lymphocyte subpopulations have established NPU concepts, which are based on common names, like “helper”, “memory”, “naïve” etc. However, due to a rapid discovery of new subpopulations and no concise understanding of the common names, a “helper, memory T-lymphocyte” (as shown in the example below) can potentially be defined with different sets of CD-markers.


To avoid misclassification based on different understanding of the terms for lymphocyte subpopulations, the CD nomenclature has been universally adopted by the scientific community and is officially approved by the International Union of Immunological Societies (IUIS). It has also been sanctioned by the World Health Organization (WHO). Due to the role of IFCC-IUPAC in the development of NPU terminology, this project seek to formalize the use of the CD nomenclature as valid term reference for creating NPU codes.


Project announcement published in Chem Int April 2022, p. 27

page last update 8 Apr 2022