Subsets of patients with aplastic anemia identified by flow microfluorometry

We used flow microfluorometry to analyze peripheral-blood mononuclear cells from 50 patients with aplastic anemia, to determine whether patients who would recover after immunosuppressive therapy could be distinguished before treatment from those who would not recover. Cells were labeled with murine monoclonal antibodies that are relatively specific for B cells, T cells, T-cell subsets, and monocytes. The data suggested that the number of lymphocytes and the ratios of various subclasses of T cells were not useful in identifying patients who were likely to recover. The complete absence of monocytes was found to identify patients who would not recover, but the presence of monocytes was also sometimes associated with lack of recovery. An unexpected finding was the significant (P less than 0.0001) association between clinical recovery and the presence of a population of small cells (4 to 8 micron) that were phenotypically associated with the erythroid lineage. If this association is confirmed, flow microfluorometry may be useful in selecting the optimal treatment for individual patients with aplastic anemia.