CD45RO

This antibody reacts with the CD45RO antigen, which is present at low density early in the T-lymphocyte maturation cycle. Upon activation by phytohemagglutinin (PHA) or alloantigen, naive T lymphocytes first acquire CD45RO and then lose CD45RA. When these activated T lymphocytes are rechallenged, the cells that exhibit a secondary response are primarily CD45RO +, leading to the concept that CD45RO + cells are a primed population of memory T lymphocytes.
In peripheral blood, the CD45RO antigen is present on approximately 40% of resting peripheral blood T lymphocytes, including the CD4 + and CD8 + subpopulations, as well as on most thymocytes and activated T lymphocytes. It is also expressed on monocytes, macrophages, and granulocytes.