Studies of human tear proteins--1. Analysis of tears from normal subjects by crossed immunoelectrophoresis.

Tears were collected from 10 normal subjects by two methods, 1) micropipetting after stimulation with an onion slice, and 2) Schirmer 1 test using a filter paper strip. The tears in the 5 x 5 mm part of the filter paper placed within the conjunctival sac were extracted with a 0.9% NaCl solution. The tear samples so obtained were analyzed by crossed immunoelectrophoresis. Nineteen proteins were identified by the use of monospecific antisera. Ten tear-specific proteins including the specific tear prealbumin of Bonavida et al., lactoferrin and lysozyme were identified by the intermediate gel method. Some differences were found in the pattern of the tear-specific proteins between the tears collected by the two methods, but the pattern was basically similar. Some individual differences were also found. The levels of serum proteins including albumin and IgG varied considerably, but it was thought to be due to dilution by reflex lacrimation during tear sampling. On the other hand, the pattern of the tear-specific proteins was fairly constant. The filter paper method allowed tear protein analysis, even in patients with 0 mm wetting by the Schirmer 1 test. A study of the length-volume relationship of the filter paper wetting showed that the tears contained in the 5 x 5 mm portion of the filter paper were about 1.8 microliters. The filter paper method was thought to offer a reliable clinical tool for the study of the tear proteins in various pathological conditions of the lacrimal secretion.