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New insights into the role platelets in antifungal host defence

Abstract number: p587

Lass-Flörl  C., Unterdorfer  S., Nussbaumer  W., Dierich  M.P.

Background: 

We observed that serotonin (5 HT) acts fungicidal against Aspergillus species and decreases fungal virulence in vitro. In humans, 5 HT is stored in platelets and the 5 HT concentration in granules is about 65 mM. These data and the coincidence of an increased infection rate and low 5 HT levels in certain diseases let us to examine the role of platelets in antifungal host defence.

Methods: 

We investigated the expression of platelets surface receptors (CD 62 P, CD 63 and CD 154) following Aspergillus (hyphae) exposition by fluorescent labelling. Platelets were mixed with fungi (ratio 100:1, 10:1) and incubated for 1 h at 37°C. Platelets activation and adherence on hyphae of Aspergillus sp. was investigated with a Zeiss DSM 950 scanning electron microscope (SEM). The XTT test was applied to assess platelets and platelets/neutrophils effects on viability. The influence on fungal growth was examined by assessing hyphal elongation. Clinical isolates of Aspergillus fumigatus (n = 2) and Aspergillus terreus (n = 2) were used for this study; each test was performed in triplicate and repeated three times.

Results: 

All Aspergillus spp. induced platelet activation as the CD 62P, CD 63 and CD 154 antigens were clearly induced and visualized by fluorescence microscopy; strain dependent expressions were observed. Spread of irregular shaped platelets over hyphal surfaces was shown by SEM. Platelets decreased the ability of hyphae to reduce XTT, co-incubation with polymorphonuclear neutrophils increased fungal damage significantly (p < 0.05). Hyphal elongation was significantly decreased (23 + 8 mm) by platelets in comparison to untreated hyphae (47 + 9 mm) after 12 h of incubation.

Conclusion: 

The impaired capacity of fungi to reduce XXT, the expression of membrane receptors and surface markers for platelet activation and the decreased hyphal elongation confirm that platelets have the potential to play an important role in host defence against Aspergillus species.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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