[Physiological protective mechanisms of the eye].

The physiological mechanisms for the protection of the eye are only partly known. It becomes increasingly evident that the eye is supervised by and included in the immune system of the body. The physiological protection system of the eye consists of a mechanical and an immunological component. The lacrimal gland plays a key role for the immune system of the anterior segment. It is part of the MALT system, and the characterisation of the special ocular components of this system-including possible homing receptors-will give important informations. Research of the ocular immune system has disclosed various special features, like the anterior chamber associated immune deviation (ACAID). The distribution of antigen presenting cells and its localization, but also the distribution of T- and B-lymphocytes is an important factor for limiting ocular inflammation. The phenomenon of 'apoptosis' seems to have an important role in maintenance of the ACAID. The cornea is nearly free of cells, and infiltrating antigen presenting cells may prevent ACAID. Research regarding mechanisms which are used to tuned these various cells will give answers to the questions how the cornea contains its optical transparency, how corneal transplant rejection works, how the eye participates in systemic disorders and may also define the role of a possible dysfunction of antigen presenting cells of the retinal pigment epithelium in senile maculopathy.