TABLE 1.

Putative host defense components of human tears and their functions

Tear component(s)	Function
Lactoferrin	Protein synthesized by the lacrimal gland; direct bacteriostatic action on bacteria
Lysozyme	Protein that targets the cell wall and causes bacteriolysis of gram-positive bacteria
β-Lysin	Causes cytolysis of bacteria resistant to lysozyme by targeting the cell membrane
Ceruloplasmin	Regulates damage to ocular tissue during inflammation
Complement	Promotes lysis of bacteria, chemotaxis, and phagocytosis in tears
Immunoglobulins	Human tears possess IgG, IgM, IgE, and IgA; IgA prevents the adherence of bacteria, modulates the normal flora, agglutinates bacteria, and can neutralize toxins