Bactericidal/permeability-increasing protein in lacrimal gland and in tears of healthy subjects.

Background: To determine the expression of bactericidal/permeability-increasing protein (BPI), a novel antimicrobial molecule, in the main lacrimal gland and its content in tears of young healthy subjects.

Methods: BPI concentration of tears was measured in 42 healthy volunteers, 13 men and 29 women, with ages ranging from 22 to 30 (mean 24.7+/-2.1) years by a time-resolved fluoroimmunoassay (TR-FIA). Immunohistochemical analysis was made to localize BPI in lacrimal gland and conjunctiva of eight autopsied subjects, two men and six women, with the age range from 44 to 87 (mean 72.3+/-14.9) years.

Result: The mean concentration of BPI in tears was 27.8+/-29.5 microg/l, and it decreased with an increase in tear flow rate (P<0.0001). There was no statistically significant difference in BPI content of tears between the genders. BPI was immunohistochemically seen in outer basal epithelial cells of intralobular and excretory ducts, squamous and basal cells of conjunctiva as well as faintly in myoepithelial cell layer of acini. The presence of BPI in the lacrimal gland and in the tear fluid was verified by Western blotting.

Conclusions: The results indicate that outer basal epithelial cells of lacrimal gland ducts contain BPI, which occurs in a relatively high concentration in tears. BPI may have a substantial antibacterial role in human tears.