Toll-like receptors — recognizing receptors of innate immune system and eyes (literature review)

    A literature review is devoted to one of the innate immunity links — the expression and functional activity of Toll-like receptors in case of ophthalmic diseases. This review consists of two parts. The first section describes the types of Toll receptors, their structure, signaling pathways, tissue distribution, functional activity and the relationship between innate and adaptive immunity by dendritic cells whose main function is the induction and regulation of T-cell response. The paper presents a «theory of risk» by P. Matcinger, which lies at the heart of understanding of the autoimmune disease mechanism.
    In the second part of the literature review there are analyzed literature sources devoted to a study of the distribution of Toll receptors in the conjunctiva, limbus, cornea, uvea, retina in normal and pathological conditions. Features of Toll receptor expression in cornea and particularly in uveal tissue are connected with an immune privileged status of the eye. The functional activity of Toll receptors may result in allergic conjunctivitis, keratitis, uveitis. A uncontrolled activation of the Toll-like receptors is potentially dangerous for the eyes, because it can lead to a unbalanced inflammation. In this regard, a negative regulation of Toll receptors can, on the one hand, inhibit their function and prevent the proper response of the innate immune system, and, on the other hand, play a significant role in the treatment of diseases caused by hyper-activation of these receptors.
    Therefore, studies of the structure, signaling pathways, expression and distribution of Toll receptors are directed not only at understanding the molecular and immunological basis of infectious and autoimmune processes, but also at a development of alternative therapies, modulating allergic and immune reactions in these processes.
    Key words: toll-like receptors, components of innate immunity, expression.