Coagulation factor XIII-A. A flow cytometric intracellular marker in the classification of acute myeloid leukemias.

The association of coagulation factors with leukocytes have been demonstrated in several previous studies. This study was designed to study the sensitivity and specificity of factor XIII subunit A (FXIII-A) labelling in cultured myeloblastic and monoblastic cell lines and to investigate the intracytoplasmic expression of FXIII-A in de novo acute myeloid leukemia (AML) samples. Myeloblastic and a monoblastic cell lines were cultured and investigated for lineage specific maturation markers and FXIII-A expression. Furthermore, FXIII-A expression was investigated in 12 normal samples (7 bone marrow and 5 peripheral blood), 86 de novo AML samples and 6 chronic myelomonocytic leukemia (CMML) samples. In the monoblastic MonoMac6 cell line the appearance of FXIII-A preceded that of CD14 while it remained negative in the myeloblastic PLB-985 cell line throughout its maturation period. Among the AML samples the average frequency of FXIII-A positive cells in myeloblastic leukemia samples was below 10%, while in M4 and M5AML samples it was above 50% and was significantly higher than the generally used CD14 marker (p < 0.0001). In the AML M4 and M5 cases, FXIII-A proved sensitive for the identification of monoblasts. FXIII-A can be considered as a reliable intracytoplasmic marker for the monocytic and megakaryocytic series and its presence is highly predictive for mono- and megakaryocytic AML and for CMML.