Immunohistochemical evaluation of lymphocyte populations in the nictitans glands of normal dogs and dogs with keratoconjunctivitis sicca.

David L Williams,Alice Tighe

doi:10.4314/ovj.v8i1.8

Abstract

Idiopathic canine keratoconjunctivitis sicca (iKCS) is a common condition of the canine eye involving a deficiency in aqueous tear production which is commonly held to have an immune-mediated, as most probably an autoimmune aetiopathogenesis. Yet to date no direct evaluation has been made of the inflammatory cell populations in the lacrimal tissue of dogs with iKCS. Here we sought to quantify T and B lymphocyte populations in the lacrimal tissue of the nictitans glands of dogs with iKCS those with neurological KCS (nKCS)and also in dogs with tear production within the recognized normal levels and no ocular surface signs of KCS. Nictitans glands were obtained from 10 healthy dogs with no signs or history consistent with KCS at post-mortem or after enucleation. Nictitans glands were also obtained at parotid duct transposition surgery from ten dogs with idiopathic KCS and three with neurogenic KCS. Histological sections form the lacrimal tissue were processed immunohistochemically with primary monoclonal antibodies recognizing the T lymphocyte CD3 antigen and the B lymphocyte CD79a antigen. Cell numbers were counted in 10 randomly sampled representative high-power fields in five sections. Statistical significance of differences in cell numbers was determined using analysis of variance with significance achieved at p=0.05.Nictitans glands from dogs with iKCS showed elevated numbers of T and B lymphocytes compared with those from dogs with normal tear production. The increase in the T cell population was highly statistically significant (p=0.0025) while the increase in B cells, while statistically significant was less pronouncedly so (p=0.049). T and B lymphocyte numbers were not significantly elevated in nictitans glands from dogs with neurogenic KCS compared with those in dogs with normal tear production. The elevation in the T cell population seen in dogs with idiopathic KCS strongly supports the widely held assumption that this disease is an immune-mediated and probably autoimmune. The lack of increase in T cell populations in dogs with nKCS strongly suggests that the changes in iKCS are causing the tear deficiency and not resulting from it.

Highlights

Idiopathic keratoconjunctivitis sicca is seen in a number of breeds of dog and is generally considered to have an immunological, and probably an autoimmune aetiopathogenesis (Williams, 2008)
By comparing nictitating membranes in dogs with Idiopathic keratoconjunctivitis sicca (iKCS) with those from neurological KCS (nKCS) animals, we aim to show that the changes in lymphocyte populations in the gland are a cause of disease rather than merely an effect of deficiency in tear production, in which case increase in inflammatory cell populations would be seen in all dry eyes regardless of pathogenesis
Statistical significance of differences in numbers of T and B cells in nictitans glands of dogs with normal tear production, dogs with iKCS and dogs with nKCS was determined by evaluating analysis of variance with significance deemed to have been reached at p=0.05

Summary

Introduction

Idiopathic keratoconjunctivitis sicca (iKCS) is seen in a number of breeds of dog and is generally considered to have an immunological, and probably an autoimmune aetiopathogenesis (Williams, 2008). While work over twenty years ago showed that the infiltrating cell population in lacrimal and nictitans glands of such dogs was lymphocytic in nature (Kaswan et al, 1984), further work characterizing these populations is lacking. One paper has evaluated the changes in lacrimal gland lymphocyte populations after the use of cyclosporine but without first characterising the cells infiltrating the gland (Izci et al, 2002). In this study we aimed to determine the immunophenotype of inflammatory cells infiltrating the tear-producing gland of the third eyelid, the nictitans gland. We compared cell numbers in the nictitans glands of normal dogs, in dogs with idiopathic KCS (iKCS) and in those with neurological KCS (nKCS) where an autoimmune pathogenesis is not central to the failure of tear production (Williams, 2008).

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