The Clinical Measurement Ontology (CMO), Measurement Methods Ontology (MMO), and Experimental Condition Ontology (XCO) are currently being developed at the Rat Genome Database. For more information about these vocabularies please see Shimoyama et al. Three ontologies to define phenotype measurement data. Front Genet. 2012;3:87. Epub 2012 May 28 or contact us (http://rgd.mcw.edu/contact/index.shtml).
Measurement of the number of lymphocytes expressing the CD4 antigen on their surface in a specified volume of whole blood. CD4 is a membrane glycoprotein found primarily on T lymphocytes, but also can be expressed on B cells, macrophages, and granulocytes. On T cells it is a co-receptor for the T cell receptor (TCR), interacts with MHC class II antigens, and functions to initiate or augment the early phase of T-cell activation.