Epsilon Open Archive

Abstract

Hypophysitis has been reported occasionally in dogs, with most cases resembling primary lymphocytic hypo-physitis in man. Although it is generally assumed that lymphocytes are not present normally in the canine pi-tuitary gland, few studies have investigated this hypothesis. However, lymphocytes are recognized in thepituitary gland of people and horses without signs of pituitary disease. It is unknown to what degree lympho-cyte infiltration of the pituitary gland might occur as an incidental finding in dogs. The aim of the present studywas to investigate the presence and distribution of lymphocytes in the pituitary gland of dogs without clinicalsuspicion of pituitary disease. Twenty dogs were subjected to routine necropsy examination. Formalin-fixedand paraffin wax-embedded sections of pituitary were stained with haematoxylin and eosin (HE) or subjectedto immunohistochemistry (IHC) using primary antibodies specific for the T-cell marker CD3 and the B-cellmarker CD79a. The number of CD3+ and CD79a+ cells per area unit (CPA) was determined for differentpituitary regions. Two dogs had extensive neoplastic lesions in the pituitary gland and were excluded fromanalysis. In the remaining 18 dogs, occasional scattered CD3+cells were found in the pituitary gland. Therewas a significant difference in CD3+CPA between pituitary regions (P¼0.001). The highest CD3+CPA wasfound in the pars tuberalis (median 41.3 cells/mm2, interquartile range 20.9e50.5 cells/mm2). In six of the 18dogs (33%), CD79a+ cells were detected in small number (median total cell number 0 cells/section, interquar-tile range 0e1.0 cells/section). This study shows that T cell, and fewer B cells, may be found in the pituitarygland of dogs without clinical suspicion of pituitary disease. Regional difference in T-cell density, with the high-est CD3+CPA in the pars tuberalis, may imply regional immunoregulatory functions in the canine pituitarygland.