This nomenclature was developed to standardize and compare
monoclonal antibodies from different sources.
Antibodies with similar reactivity patterns are assigned to CD groups representing "clusters of differentiation."
T lymphocytes are CD3+ and can be separated into the CD4+ T helper cells and the CD8+ cytotoxic/suppressor cells. Although CD4+ cells are predominantly
T lymphocytes, some monocytes are also CD4+.