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Blood, 15 December 2008, Vol. 112, No. 13, pp. 4784-4785.
UV-C irradiation gives platelets a sunburnUNIVERSITY OF PENNSYLVANIA
In this issue of Blood, Verhaar and colleagues report that, although UV-C irradiation is an attractive method to minimize microbial contamination of platelet concentrates, it directly activates platelet
Bacterial contamination of blood products can result from inadequate skin cleansing, from a small core of skin that sometimes enters the phlebotomy needle, and from contaminated blood collection packs.3 Thus, obvious ways to reduce contamination are to improve skin disinfection, to discard the first 15 to 30 mL of collected blood, and to culture or otherwise screen platelet products for the presence of bacteria.3 Another approach is to inactivate the contaminating bacteria. Photodynamic and photochemical methods using ultraviolet (UV) light have been developed to inactivate bacteria in platelet products by damaging their DNA and RNA. Thus, irradiating platelet concentrates containing psoralen derivatives with UV-A light (wave length 315-400 nm) induces pyrimidine crosslinks in bacterial DNA and RNA, preventing subsequent replication and transcription. In the SPRINT trial, transfused platelets that had been irradiated with UV-A in the presence of the psoralen amotosalen were as hemostatically effective as control platelets. However, the photochemical treatment resulted in lower platelet increments and shorter intervals between transfusions, suggesting that it had caused mild platelet injury.4 Although UV-B irradiation (wave length 280-315 nm) has been used primarily to prevent HLA sensitization and platelet refractoriness, it has been combined with the dye thionine and yellow light in a 2-step procedure to inactivate bacteria in platelet concentrates.5 Enthusiasm for UV-B as a decontaminant, however, must be tempered by the report by van Marwijk Kooy et al, which found that UV-B irradiation causes platelet aggregation via oxygen radical-induced activation of protein kinase C.6
In contrast to UV-A and UV-B, UV-C irradiation (wave length 100-280 nm) reduces bacterial growth in platelet concentrates without the need for photosensitizing additives. However, Terpstra et al observed that when platelets suspended in 10% plasma were irradiated with UV-C light, there was dose-dependent LDH release, P-selectin expression, and phosphotidylserine exposure that was mitigated to some extent by increasing the plasma concentration to 30%.7 In the work reported in this issue of Blood, the same group of investigators has studied the mechanism responsible for the decrease in platelet count that occurs during storage of UV-C–treated platelets. They found that relatively high-dose UV-C irradiation (1500 J/m2) caused immediate, The bacteriocidal properties of UV-C radiation would make it seem an ideal solution for the infectious complications of platelet transfusion. But the chemistry responsible for its bactericidal properties also has unexpected but unavoidable novel consequences on platelet function. It's not easy to mess with Mother Nature.
Footnotes
Conflict-of-interest disclosure: The author declares no competing financial interests.
REFERENCES
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| Copyright © 2008 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
IIbβ3 by reducing critical extracellular disulfide bonds, resulting in the aggregation of stored platelets. 