The rheological properties of human leukocytes (WBCs) have been studied using the micropipette aspiration and the filtration technique. Partial micropipette (i.d. 2.8–4.5
\mu
m) aspiration of individual leukocytes under constant aspiration pressure of 8 mm H
_{2}
O and measurement of the aspirated length as a function of time (creep experiments) according to the Evans model have been carried out and the apparent viscosity
\mu_{\mathrm{app}}
was estimated. In the filtration experiments, using the Hemorheometer, the Index Rigidity of Leukocytes, ILR, was also estimated. The apparent viscosity
\mu_{\mathrm{app}}
of normal PMN and MNC was significantly different
p< 0.05)
, while the LYM and PMN had no statistical difference
(p<0.5)
. The leukocytes of the cell line HL‐60 were more rigid than the normal PMN
(p <0.01)
, while the PMN from patients with type II diabetes mellitus were more rigid than the normal PMN
(p < 0.005)
. The results of IRL showed similar differences among all of the leukocyte subpopulations. Comparison of these findings suggests a possible relationship between ILR and
\mu_{\mathrm{app}}
which in this case is:
\mathrm{ILR} = 598 + 0.54\ \mu_{\mathrm{app}}\ (r = 0.986
,
p
‐value 0.0003).
