The expression of the different CD45 isoforms depends on cell type and state of differentiation and activation (e.g., naïve CD4+CD45RA+ T cells, and memory CD4+CD45RO+ T cells); it is also very interesting the association between CD45 polymorphisms and susceptibility or resistance to infective or autoimmune diseases [71]. The gene discussed is PTPRC; the disease is autoimmune disease.