LACK OF CLINICALLY SIGNIFICANT CONTACT SYSTEM ACTIVATION DURING PLATELET CONCENTRATE FILTRATION BY LEUKOCYTE REMOVAL FILTERS

When blood (plasma) contacts certain foreign surfaces, factor XII can activate and trigger a series of reactions leading to cleavage of kini nogens with subsequent release of bradykinin. In this study, we invest igated two different widely used leukocyte removal filters, Pall PXL8K (A) and Asahi PLS-5A (B), to test whether clinically significant cont act activation occurred during leukodepletion of platelet-rich plasma (PRP). Kininogens were measured by particle concentration fluorescence immunoassay (PCFIA), which can detect cleavage of high and low molecu lar weight kininogens (HK and LK), the parent molecules of bradykinin, to determine if contact activation had occurred. A slight, nonsignifi cant decrease in HK and LK was observed with filter A after the first 5 mL was filtered that returned to prefiltration levels by the end of the filtration. Specific TotK (the combined measurement of HK and LK h eavy chains divided by plasma protein concentration) showed a small, s ignificant decrease with filter A after the first 5 mt of platelet con centrates was filtered that returned to prefiltration levels by the en d of the filtration. There were no significant increases or decreases in the cleaved kininogen index (CKI), an index of HK proteolytic activ ation or HK and LK destruction (with release of bradykinin). These dat a suggest that small amounts of both HK and LK initially adsorb to fil ter A and then desorb, primarily intact. These data also indicate that no significant contact activation, as measured by PCFIA, occurs durin g leukodepletion of platelet concentrates with either filter A or B. ( C) 1998 by The American Society of Hematology.