Features of the Immunologic Microenvironment

The conjunctiva shares many of the features typical of mucosal sites. It is well vascularized and has good lymphatic drainage to preauricular and submandibular nodes. The tissue contains numerous Langerhans cells, other dendritic cells, and macrophages that serve as potential antigen-presenting cells (APCs). Conjunctival follicles that enlarge after certain types of ocular surface infection or inflammation represent collections of T lymphocytes, B lymphocytes, and APCs. By analogy with similar sites, such as Peyer patches of the intestine, these follicles are likely sites for localized immune processing of antigens that permeate through the thin overlying epithelium.

The conjunctiva, especially the substantia propria, is richly populated with potential effector cells, predominately mast cells. All antibody isotypes are represented, with IgA as the most abundant type in the tear film. Local antibody production presumably occurs as well as passive leakage. Soluble molecules of the innate immune system, especially complement, are also present. The conjunctiva appears to support most adaptive and innate immune effector responses, especially antibody-mediated and lymphocyte-mediated responses, although IgE-mediated mast-cell degranulation is one of the most common and important. See also BCSC Section 8, External Disease and Cornea, for further information on conjunctival immune responses.

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.