Figure 7.

Interaction of human platelets with C. albicans during whole-blood infection is influenced by complement opsonization. (A) The percentage of extracellular C. albicans during human whole-blood infection was investigated via flow cytometry and calculated relative to total fungal cells in blood (set to 100%) of five independent experiments with blood from different donors. A steady reduction of extracellular fungi over time was observed (1-Way ANOVA and Test for linear trend, p<0.0001). (B) Less than 10% of extracellular C. albicans cells showed a CD42b⁺ staining at each time point, reflecting a low platelet binding to C. albicans in human whole-blood (n = 5). (C) Isolated human platelets were confronted with C. albicans either in the presence of non-treated (active plasma) or heat-inactivated autologous plasma (inactive plasma). Co-incubation in medium containing active plasma prevented the time-dependent increase in platelet-C. albicans interaction as observed for heat-inactivated plasma. Significantly less CD42b-positive fungal cells were observed with active compared to inactive plasma at each time point (unpaired, two-tailed t-test, p<0.0001, n = 7). (D) C. albicans cells were either pre-incubated in non-treated (C3b-opsonized C. albicans) or heat-inactivated autologous plasma (non-opsonized C. albicans, no surface C3b) before confrontation with isolated human platelets in medium with inactive plasma for 1 h. Opsonization of C. albicans resulted in a markedly lower association with platelets compared non-opsonized C. albicans (p = 0.035, unpaired, two-tailed t-test).