Summary
Blood coagulation factor XIII (FXIII) is a protransglutaminase circulating asa tetramer
formed by two types of subunits (A2B2). The intracellular dimeric form of FXIII (A2) is present in platelets, megakaryocytes, monocytes and macrophages and has been
detected in mono-and megakaryocytic leukemias. The aim of our study was to investigate
FXIII-A expression in newly diagnosed B cell acute lymphoblastic leukemia (ALL) samples.
We examined 47 de novo ALL cases of B cell origin by triple color labeling with flow cytometry. FXIII-A
was detected by a FITC conjugated monoclonal antibody combined with CD34 and CD45
staining. In selected cases FXIII-A was investigated on slides prepared from blasts
and visualized with a fluorescent microscope. In addition, blasts were studied by
Western blot analysis and FXIII-A was measured by a highly sensitive ELISA method.
By flow cytometry 19 samples of the 47 cases were found to be FXIII-A positive. Antigen
concentration was 3.11± 1.19 fg/blast, while normal lymphoid precursors and mature
lymphocytes from B-CLL did not contain FXIII-A. In the lysate of lymphoblasts that
were positive by flow cytometry, a single band (82 kDa) corresponding to FXIII-A was
detected on Western blots. Confocal laser scanning microscopic examination revealed
the presence of FXIII-A in the cytoplasm of these lymphoblasts. This novel expression
site of FXIII-A in leukemic lymphoblasts can be utilized as a diagnostic tool and
may also gain functional significance in B-lineage ALL.
Keywords
Coagulation factor XIII - acute lymphoblastic leukemia - flow cytometry