Proteins in tears from healthy and diseased eyes

The levels of total protein in tears from healthy donors, conjunctivitis vernalis patients, and conjunctivitis follicularis patients, were 625, 1370 and 1160 mg% respectively. Serum albumin accounted for 3.3%, 43% and 67% of the total protein of tears from these groups, and the level of proteins probably synthesized by the lacrimal gland, was in tears from conjunctivitis follicularis patients only half the level in normal tears. By crossed immunoelectrophoresis with intermediate gel, 10 antigenic species could be recognized in normal tears, and of these the following were identified: Lysozyme, IgA, lactoferrin and serum albumin. In tears from patients with conjunctivitis vernalis three more immunoprecipitates were observed, of which one was due to IgG. No lysozyme could be demonstrated in tears from a case of conjunctivitis sicca by immunoelectrophoresis. In tears from healthy donors the mean level of IgA was 20 mg%, of IgG 3 mg%, and IgM could not be demonstrated. Rabbit anti-tear immunoglobulin did not precipitate a standard of human IgM in double immunodiffusion. In cases of conjunctivitis vernalis and follicularis the mean levels were increased to 80 and 114 mg% IgG, and 11 and 14 mg% IgM, but IgA was increased only to 32 and 41 mg%. It is assumed that the level of IgA in normal tears is almost entirely due to local synthesis, while serum albumin and other immunoglobulins may have escaped from the circulation by molecular sieving. The increased levels of immunoglobulins in inflammatory diseases is probably due to transudation. However, in blepharoconjunctivitis patients several tear samples with a high IgM and a low or zero level of IgG could be demonstrated. Possible explanations for this phenomenon are discussed.