Relationships between levels of lysozyme, lactoferrin, salivary peroxidase, and secretory immunoglobulin A in stimulated parotid saliva

Recent studies suggest that salivary lysozyme (Lz), lactoferrin (Lf), peroxidase (Spx), and secretory immunoglobulin A (sIgA) may interact in a common antimicrobial system. A multiple protein approach therefore may be needed to determine the role of this system in oral health and ecology. In the present study we investigate the relationships between levels of Lz, Lf, Spx, and sIgA (adjusted for flow rate and total protein) in stimulated parotid saliva from 44 dental students. Principal components analysis was used to determine major patterns of intercorrelation between variables; cluster analysis was used to identify groups of subjects with similar salivary profiles for Lz, Lf, Spx, and sIgA. Spx tended to vary independently of Lz and Lf, which, in turn, tended to vary together. sIgA showed a weak negative relationship with Spx and a weak positive relationship with Lz and Lf. Six major clusters of subjects with similar antimicrobial protein profiles were found. These were significantly different at P < 0.0001. Spx was the most important determinant of cluster membership followed (in order of importance) by Lz, Lf, and sIgA. Cluster profiles were Spx^-, sIgAμ, Lf^-, Lz^-; Spx^-, sIgA⁺, Lfμ, Lz⁺; Spxμ, sIgAμ, Lfμ, Lzμ; Spx⁺, sIgA^-, Lf^-, Lz^-; Spx⁺, sIgAμ, Lf⁺, Lz^-; and Spx⁺, sIgAμ, Lf⁺, Lz⁺ (-, μ, and + refer to the position of the cluster mean for each variable relative to the overall mean for that variable). Results suggest that clusters may be a product of independent variation in the secretory activity of acinar and intercalated duct cells.