The eye is linked to the common mucosal immune system. This system play the part in preservation of the ocular surface. Tear fluid contains pro and anty-inflammatory factors such as lactoferrin, plasmin, immunoglobulins, and a lot of cytokines (interleukins, GM-CSF, TGF alfa and beta). The cornea is immunologicaly preferred, as a result of lack of resident lymphoreticular cells.