To study the effects of platelets on macrophages phagocytosis and inhibition of fungi.

Macrophages were cultured, Fusarium Pythium spores were extracted and platelets were isolated from blood of mouse.Simple spore group, spore+ macrophage group and mixed platelet group were set, and were inoculated with fungal spore, equal proportion spore+ macrophage and platelet+ spore+ macrophage, respectively.The prepared plate was placed on a spinning disk laser scanning confocal microscope at 1 hour, 2, 3 and 4 hours after culture, five visual fields were randomly selected at the corresponding time points for photography.The phagocytic rate, phagocytic index and fungal spore germination rate were calculated.Fungal hyphae length of each group at 4, 6 and 8 hours after culture were calculated.The single macrophage group, spore+ macrophage group and mixed platelet group were set and the cytotoxicity was measured by real-time cell analyzer.The breeding and use of mice was in according with the ARVO statement.This study was approved by the Experimental Animal Ethics Committee of Henan Eye Institute (HNEECA-2017-04).

The phagocytic rate and phagocytic index of macrophages in mixed platelet group at 1 hour, 2, 3 and 4 hours after culture were significantly higher than those in spore+ macrophage group at corresponding time point (all at P<0.05). There were significant differences in spore germination rate at 1 hour, 2, 3 and 4 hours after culture among different groups (H=60.05, 37.89, 55.15, 60.52; all at P<0.001). The spore germination rates of spore+ macrophage group at 1 hour, 2, 3 and 4 hours after culture were lower than those of simple spore group, while the spore germination rates of mixed platelet group at 1 hour and 3, 4 hours after culture were lower than that of spore+ macrophage group, the differences were statistically significant (all at P<0.01). There were significant differences in fungal hyphae length at 4, 6 and 8 hours after culture among the three groups (H=13.76, 43.57, 60.87; all at P≤0.001). The fungal hyphae lengths of spore+ macrophage group at 4, 6 and 8 hours after culture were lower than those of simple spore group, and the fungal hyphae lengths of mixed platelet group at 6 and 8 hours after culture were lower than those of spore+ macrophage group at the corresponding time point.The differences were statistically significant (all at P<0.05). There was no significant difference in cell index between 0 hour, 6, 12, 18 and 24 hours after culture (F=0.02, 1.08, 1.61, 1.58, 2.52; all at P>0.05). There were significant differences in cell index among different groups at 30, 36, 42 and 48 hours after culture (F=10.81, 8.08, 5.61, 5.72; all at P<0.05). The cell indexes in spore+ macrophage group at different time points were significantly lower than those in simple macrophage group (all at P<0.01).

Platelets can promote the phagocytosis and inhibition of macrophages on fungi, and platelets may have antagonistic effect on fungal cytotoxicity.

Keratitis/pathology; Macrophage; Fungi; Platelets; Phagocytosis; Germination rate