Cellular inflammatory response induced by sensory denervation of the conjunctiva in monkeys

Abstract

The inflammatory response induced by sensory denervation of the cornea, neuroparalytic (neurotrophic) keratitis, has been widely reported in the literature. Clinical evidence has shown that the conjunctiva also responds to sensory denervation, but little is known of the cytology of the conjunctival tissue response to denervation. The purpose of this study therefore was to investigate the cytological aspects of tissue response induced in the conjunctiva of monkeys by sensory denervation. Intracranial ophthalmic neurotomy was carried out in three monkeys, maxillary neurotomy in four, combined ophthalmic and maxillary neurotomy in two, and infraorbital nerve transaction in one monkey. These various operations were performed for other experimental purposes, but the conjunctival tissues from the animals were suitable and available to study the cytology of the inflammatory response induced in the tissue following the sensory denervation. The cytological changes were studied using light microscopy. Complete or severe ophthalmic nerve transection induced significant inflammatory responses, which were largely confined to the tarsal region of the conjunctiva. The responses included a substantial increase in the infiltration of the epithelium by polymorphonuclear leucocytes and severe disruption of the epithelium. The number of macrophages in the conjunctiva also increased. The response induced by maxillary denervation, however, was not as pronounced as that induced by sensory denervation. The restriction of the conjunctival tissue response to the tarsal region was considered to be due to the friction between the tarsal conjunctiva (and the hard tarsal plate) and the cornea during blinking. This study shows that sensory denervation of the conjunctiva elicits an inflammatory response characterized by substantial infiltration of the epithelium by neutrophil and macrophage and disorganization of the conjunctival tissue.

Fig. 1

Section of the tarsal conjunctiva showing inflammatory cells (arrowhead) in the epithelium. Most of the cells were neutrophils. The lobulated nuclei could just be seen. Large spaces (s) without inflammatory cells were present in the epithelium. Various inflammatory cells, including plasma cells (arrow), were present in the stroma. (Ophthalmic neurotomy, 8 days.) Scale bar, 2.4 µm.

Fig. 2

Section of the tarsal conjunctiva showing seven neutrophils in a vacuole in the epithelium. The vacuoles also contained colloidal fluid which was quite evident in another cell membrane-bound superficial vacuole (arrow) containing one neutrophil. Inflammatory cells in the epithelium were mostly neutrophils. Other cell types are present in the stroma. (Ophthalmic neurotomy, 7 days.) Scale bar, 2.4 μm.

Fig. 3

Section of tarsal conjunctiva showing three macrophages in the epithelium (arrow). Large empty spaces (s) bounded by strands of epithelial cytoplasm were present in the epithelium. (Ophthalmic neurotomy, 8 days.) Scale bar, 2.4 µm.