The effect of saliva on the interaction between microorganisms and polymorphonuclear leukocytes (PMNs) or HL-60 cells

Saliva and polymorphonuclear leukocytes (PMNs) are both important players in the innate defense of the oral cavity, but little is known of the effect of saliva on PMN function. In this study, we investigated the effect of saliva on the adhesion of Fu-sobacterium nucleatum and Candida albicans to human granulocytic-differentiated HL-60 cells. The adhesion of FITC-labeled F. nucleatum and C. albicans to HL-60 cells was performed in solution in the presence of clarified human whole saliva (CHWS) or parotid saliva, followed by flowcytometric analysis. In the presence of saliva, the adhesion of C. albicans to HL-60 cells was enhanced, while the adhesion of F. nucleatum was inhibited. The adherence of C. albicans was higher to CHWS and parotid saliva-treated HL-60 cells than to untreated cells. Adherence of F. nucleatum was lower to CHWS-treated HL-60 cells. Pretreatment of C. albicans with CHWS enhanced the adherence to HL-60 cells. Pretreatment of F. nucleatum with saliva did not affect the adhesion of F. nucleatum to HL-60 cells. The peptide statherin inhibited the adhesion of F. nucleatum to HL-60 cells, but did not affect the interaction between C. albicans and HL-60 cells. In conclusion, we found that saliva modulates the adhesion of oral microorganisms to HL-60 cells in different ways. Statherin inhibits the adhesion of F. nucleatum to HL-60 cells, but another protein enhances the adhesion of C. albicans to HL-60. Perhaps different proteins contribute to enhanced or inhibited microbial adhesion to PMNs.