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 HI130 monoclonal antibody specifically reacts with the 180 kDa，190 kDa，205 kDa，and 220 kDa isoforms of the human leukocyte common antigen (LCA) CD45. It is expressed on lymphocytes，granulocytes，monocytes，thymocytes，and eosinophils，but not on mature erythrocytes，platelets，mature erythroid cells of bone marrow，and non-hematopoietic tissues. CD45 is essential for T cell activation and the tyrosine phosphatase activity of its intracellular region is integral for signal transduction.
