The conjunctiva contains mucosa-associated lymphoid tissue (MALT), an interconnected network of mucosal sites in the body (the epithelial lining of the respiratory tract, gut, and genitourinary tract, and the ocular surface and its adnexae) that share certain immunologic features:
large number of APCs
specialized structures for localized antigen processing
unique effector cells (eg, intraepithelial T lymphocytes and abundant mast cells)
The most distinctive feature of MALT is the homing of effector T and B lymphocytes to all MALT sites after immunization at one site. This migration occurs because of the shared expression of specific cell-adhesion molecules on postcapillary venules of the mucosal vasculature. MALT immune response arcs favor T helper-2 (Th2)–dominated responses that result in the production of predominantly immunoglobulin A (IgA) and IgE antibodies. Processing of soluble antigens through MALT, especially in the gut sites, often produces immune tolerance, presumably by activating Th2-like regulatory T lymphocytes that suppress T helper-1 (Th1)–delayed hypersensitivity (DH) effector cells.
Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.