LEUKOCYTE FILTERABILITY - COMPARING DILUTED WITH UNDILUTED BLOOD

Red blood cells and about 95% of white blood cells have an immediate a nd constant effect on the flow of undiluted or diluted blood through 5 mu m filters. The remaining 5% of all leucocytes exert an increasing influence on flow such that the rate of flow of diluted and undiluted blood through these filters is continually declining over a period of 150 s. Analysis of this declining now rate enables these cells to be c ounted and their rheological properties to be deduced. Approximately 5 0% of these slow leucocytes pass through the filters with a transit ti me of about 30 s and the remaining cells act as pore blockers for 150 s. The numbers and flow properties of slow leucocytes was approximatel y the same in blood from young women (25 years) and older men (65 year s). However, the number of slow leucocytes was increased in a group of men (65 years) suffering from peripheral arterial occlusive disease, Dilution of the blood with phosphate-buffered saline increased the num bers of slow leucocytes in both of the older, but not the younger, gro up of volunteers. This effect was particularly noticeable in the patie nt group. It is recommended that filtration studies of the rheological profile of leucocytes can, and must, be performed with undiluted bloo d. The properties after dilution may sometimes, but not invariably, re flect changes ex vivo as well as inherent differences in the cells the mselves.