Introduction. During haemodialysis (HD), an early and transient white
blood cell (WBC) reduction is noted in the peripheral blood, which has
been attributed mainly to the sequestration of polymorphonuclear cell
s (PMN) in the pulmonary vasculature. However, WBC also adhere to the
dialyser, as demonstrated before in an elution study performed after H
D. In the present study, we investigated if intradialyser WBC sequestr
ation contributes to the WBC nadir in the blood shortly after the star
t of HD and whether or not different mechanisms underlie PMN adherence
in dialyser and lung. In addition, PMN degranulation was analysed not
only in peripheral blood but also in dialyser eluates (DE). Subjects
and methods. Dialysers were eluted after 71/2 (DE-71/2) and 180 (DE-18
0) min of HD in eight patients. Blood samples were taken before HD (tO
), and at t71/2 and t180. Besides WBC count and differentiation, PMN a
dhesion (CDllb and CD62L) and degranulation markers (CD63 and CD66b) w
ere assessed by flow cytometry. Results. In the blood, a WBC fall was
noted at t71/2 (from 5.8 to 4.8 x 10(9)/l; absolute about 5 x 10(9) ce
lls). DE contained 3.0 x 10(6) cells at t71/2, and 57.2 x 10(6) at t18
0 (P=0.015). As for CDllb, at t71/2 both in the blood and DE an increa
sed expression was observed, as compared to tO (P=0.01); CDllb express
ion in DE-71/2 was higher than in DE-180 (P=0.025). In contrast, CD62L
showed downregulation only in DE both at t71/2 (mean fluorescence int
ensity (MFI) PB 4172 and DE-71/2 2353, P=0.01), and at t180 (MFI 794,
P=0.03 versus DE-71/2), when compared to blood at tO. As for degranula
tion markers, an increase was observed in blood at t71/2 (MFI CD63 fro
m 357 to 506, P=0.02; CD66b from 507 to 794, P=0.001), in comparison w
ith tO. fluted PMN at t71/2 showed a higher expression of CD63 than PM
N in blood at t71/2 and DE-180 (MFI in DE-71/2 1280 and blood 506, P=0
.003). The expression of CD66b was increased in DE-7% (MFI 1803 versus
blood 794, P=0.01), and even more in DE-180 (MFI 2763, P=0.002), when
compared to blood. Conclusions. From these data it is concluded first
, that intradialyser PMN sequestration does not contribute markedly to
the WBC nadir in the circulation. Second, intradialyser PMN trapping
appears to result primarily from non-adhesion-molecule-mediated factor
s, as indicated by an increased expression of CDllb at t71/2 on eluted
PMN associated with low cell numbers in DE, and normalized CDllb expr
ession at t180 associated with considerably higher cell numbers in DE.
Third, HD-induced degranulation seems to be a complex phenomenon. Aft
er a rapid transient onset, characterized by an early upregulation of
CD63 and CD66b on PMN leaving the dialyser, degranulation continues wi
thin the device as indicated by an additional rise in the expression o
f CD66b on PMN in DE-180.