HUMAN PLATELETS DAMAGE ASPERGILLUS-FUMIGATUS HYPHAE AND MAY SUPPLEMENT KILLING BY NEUTROPHILS

Neutropenia is considered a significant risk factor for invasive asper gillosis but is almost always associated with concurrent thrombocytope nia. Studies determined that platelets, like neutrophils, attached to cell walls of the invasive hyphal form of Aspergillus fumigatus. Organ isms were damaged as shown by loss of cell wall integrity in scanning laser confocal microscopy and release of defined hyphal surface glycop roteins. Rapid expression appearance of surface antigen CD63 and relea se of markers of platelet degranulation confirmed activation during at tachment to hyphae. Optimal platelet activation required opsonization of hyphae with fresh or heat-inactivated whole plasma. These effects o f opsonization with whole plasma could not be duplicated by pooled hum an serum, immunoglobulin G, or fibrinogen, whether used separately or combined. Thus, platelets in the presence of whole plasma have the pot ential to play an important role in normal host defenses against invas ive aspergillosis.