Granulocytes from patients with paroxysmal nocturnal hemoglobinuria and normal individuals have the same sensitivity to spontaneous apoptosis.
OBJECTIVE
The aim of this study was to determine whether granulocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) are more or less intrinsically sensitive to spontaneous apoptosis than granulocytes from healthy individuals. Resistance to apoptosis has been suggested as an explanation for the proliferation or selection of PNH clones.


METHODS
Peripheral blood granulocytes from five patients with PNH, five patients with myelodysplastic syndrome (MDS), and five healthy volunteers were cultured in the absence of serum. Spontaneous apoptosis of the granulocytes was assessed every 6 hours by flow cytometry. The expression levels of CD16b, CD95, and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor also were studied by flow cytometry, and caspase-3 activity was measured by fluorometry.


RESULTS
There were no significant differences in the proportion or absolute numbers of apoptotic and apoptotic/dead granulocytes between the cells from PNH patients and healthy individuals, whereas those from MDS patients showed significantly lower frequencies of apoptotic granulocytes compared with normal controls. The proportion of CD16b(-) granulocytes was not significantly different among the three groups during in vitro culture. CD95 and GM-CSF receptor was not significantly increased in cultured granulocytes or noncultured granulocytes from, respectively, patients with PNH and normal controls. Caspase-3 activity significantly decreased in cultured granulocytes from MDS patients, but not in granulocytes from PNH patients.


CONCLUSIONS
Granulocytes from PNH patients did not display a reduced sensitivity to spontaneous apoptosis, suggesting that the apoptosis of blood cells in PNH may not be an important factor in proliferation or selection of PNH clones. These findings are in agreement with the normal lifespan of granulocytes in vivo.
Yamamoto
Tetsuo
T
First Department of Internal Medicine, Fukushima Medical University, Fukushima, Japan.
Shichishima
Tsutomu
T
Shikama
Yayoi
Y
Saitoh
Yurie
Y
Ogawa
Kazuei
K
Maruyama
Yukio
Y
D000328:Adult; D000368:Aged; D017304:Annexin A5 / Q000097:blood; D000911:Antibodies, Monoclonal; D017209:Apoptosis; D018957:CD59 Antigens / Q000097:blood; D053148:Caspase 3; D020169:Caspases / Q000097:blood; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004912:Erythrocytes / Q000276:immunology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006098:Granulocytes / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009190:Myelodysplastic Syndromes / Q000097:blood; D011419:Propidium; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000097:blood; D017452:Receptors, IgG / Q000097:blood; D019014:fas Receptor / Q000097:blood
D017304:Annexin A5; D000911:Antibodies, Monoclonal; D018957:CD59 Antigens; D016895:Culture Media, Serum-Free; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D017452:Receptors, IgG; D019014:fas Receptor; D011419:Propidium; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases