K562 cells were the first human immortalised myelogenous leukemia line to be established. K562 cells are of the erythroleukemia type, and the line is derived from a 53-year-old female chronic myelogenous leukemia patient in blast crisis. The cells are non-adherent and rounded, are positive for the bcr:abl fusion gene, and bear some proteomic resemblance to both undifferentiated granulocytes and erythrocytes. Two sub-lines are available which express MHC class-I A2 and A3.