Fig. 2: Tissue changes in trachoma.

Schematic of the histology of the normal conjunctiva, the conjunctiva in the presence of active trachoma and conjunctiva in the presence of trachomatous scarring. a | The normal conjunctiva has a non-keratinized, stratified epithelium of 3–5 cell layers, containing interspersed goblet cells that secrete mucin. The tear film covers the epithelium. The deeper lamina propria accommodates blood vessels, lymphoid cells and other connective tissue elements. b | When infected with Chlamydia trachomatis, inflammation is manifest through telangiectasia of capillaries and small venules, and a mixed inflammatory cell infiltrate. Collections of B cells, T cells and macrophages form lymphoid follicles in the lamina propria; B cells form the core and the bulk of their mass. When sufficiently large, lymphoid follicles distort the contour of the overlying epithelium (not shown) and can be seen in the everted tarsal conjunctivae. c | In the scarred conjunctiva, goblet cells are depleted. The tear film is reduced in volume and changed in composition. An increasingly disorganized scar is found in the lamina propria. Scars may also be found in the tarsal plate (not shown). ECM, extracellular matrix.