CD45，a transmembrane multifunctional glycoprotein，is a member of Type I receptor-linked PTPase family and is expressed as multiple isoforms due to alternative splicing. Expression of these isoforms is highly regulated and shift in this expression determines T-cell activation. CD45RB consists of exon B and is predominantly expressed in naïve T-cells secreting IL-2. Its expression is low in primed/memory T cells，cells that express Th2 cytokines such as IL-4 and IL-10 and population of T-cells with regulatory function. Immunotherapy with CD45RB antibody is being widely studied in transplantation and vaccination. CD45 antibodies are commonly used to identify tumors of lymphoid origin. The UCHL1 monoclonal antibody specifically reacts with human CD45RO，a 180 kDa isoform of the leukocyte common antigen CD45. CD45RO is a transmembrane glycoprotein with tyrosine phosphatase activity and is expressed by majority of thymocytes，monocytes，granulocytes，and activated memory T lymphocytes. The subsets of peripheral T lymphocytes can be discriminated by using the CD45RO and CD45RA expressing cells.
