Examples of immunophenotype changes at relapse, compared to diagnosis.

Bivariate displays of forward and side scatter (FSC, SSC) and of coexpression of 2 antigens are shown. Leukemia gates are shown in the forward- versus side-scatter displays. Lines in bivariate displays of antigen coexpression are positioned to define positive and negative regions based on binding of isotype controls. Panel A illustrates a population change at relapse. At diagnosis a single population was present that expressed CD15 and CD11b homogeneously and CD13 heterogeneously, and did not express CD34. At relapse, there was homogeneous expression of CD13 and heterogeneous expression of CD34, with complete absence of CD15 and CD11b expression. The populations present at diagnosis and at relapse are different; there is loss of the original population and appearance of a different population. Panel B illustrates antigen change at relapse. Gain of CD2 and loss of CD56 are seen at relapse on a population with bright CD34 expression, present both at diagnosis and at relapse.