Background: Most studies of flow cytometry have been limited to the analysis of cell
surface antigen. However, antigens on virtually any intracellular organ or structure could
be candidates for use of flow cytomeoy. The development of a fixation procedure
allowed flow cytometric analysis of nuclear and other intracellular antigens, especially in
leukemia. We describe a simple and rapid method for detection of intracellular antigens
of leukemic cells by flow cytometry.
Methods: Three fixatives, buffered formaldehyde acetone(BFA), ethanol, and
paraformaldehyde with methanol, were studied for their effectiveness to detect
intracellular cytoplasmic IgM heavy chain(Cμ), or terminal deoxynucleotidyl
transferase(TdT). The results were compared with those of conventional fluorescent
microscopic method utilizing cytospin.
Results: Forty seven cases of leukemic patients were studied. Out of 24 ALL patients,
6 cases of Cμ were detected by flow cytometric method, and 3 were detected by
fluorescent microscopic method.
For TdT nuclear antigens, 31 cases out of all 47 leukemia were detected by flow
cytornetry, and 20 cases by fluorescent microscopy. Among the fixatives studied, BFA
showed excellent preservation of cellula scattergram and was easy to use for the
detection of intacellular antigens.
Conclusion: In our experiment, the flow cytometric method is more sensitive than the
fluorescent microscopic method. And the flow cytometric method has the advantages of
easy standardization, less labor, and less observer-dependent.

Keywords: Flow cytometry, Intracellular antigen, Buffered formaldehyde acetone