Hemodialysis neutropenia correlates with a decreased filterability and an increase in the number of cytoplasmic actin filaments in peripheral blood neutrophils, which is preceded by a decrease in the number of surface expression of L-selectin

In order to clarify the precise cellular mechanism of hemodialysis neutrope nia, we examined the changes in the viscoelasticity of peripheral blood neu trophils using both the micropore and the microchannel filtration methods, and the changes in the neutrophil surface expression of Mac-1, L-selectin a nd sialyl Lewis X and the cytoplasmic expression of the actin filaments usi ng a flow cytometric analysis during a dialysis session. Five patients with chronic renal failure were selected who showed a nadir leukocyte count in peripheral blood at 30 min after the initiation of the dialysis session. Th e neutrophil count also reached a nadir st 30 min and thereafter returned t o almost the predialysis level by 180 min. Both the micropore filtration ti me and the microchannel passage time, which reflect the viscoelasticity of the peripheral blood neutrophils, correlated inversely with the neutrophil count. At the nadir of neutropenia, the neutrophils were observed to have b ecome both adhesive and viscoelastic. The actin filaments in the neutrophil cytoplasm gradually increased in number from the start of dialysis, reachi ng a peak level at 30 min, and thereafter decreasing to predialysis levels. The Mac-1 expression continuously increased up from 30 min until the end o f dialysis. The L-selectin expression first decreased at 15 min, but therea fter returned to predialysis levels within 60 min. The SLe(x) expression di d not change throughout the course of the session. These results th us indi cated the neutrophil counts during a dialysis session to inversely correlat e with the viscoelasticity of the neutrophils expressed by the micropore fi ltration rime or microchannel passage time, which possibly depends on the c ontents of cytoplasmic actin filaments. In addition, the shedding of L-sele ctin from neutrophil surface may also be involved in the first step of hemo dialysis neutropenia.