PHENOTYPIC CHARACTERIZATION OF INTESTINAL LYMPHOCYTES IN-OVINE PARATUBERCULOSIS BY IMMUNOHISTOCHEMISTRY

Characterisation of the T-cell subsets in intestinal lesions in sheep with paratuberculosis may contribute to our understanding of the patho genesis of this disease. To determine the phenotype and distribution o f lymphocytes in the normal sheep intestinal mucosa and in Mycobacteri um avium subspecies paratuberculosis infected sheep, immunohistochemis try was performed on 12 normal sheep and 18 naturally infected, clinic ally diseased sheep of which 12 showed lepromatous and six tuberculoid forms of the disease. Immunoperoxidase staining was carried out on fr ozen sections of ileum using monoclonal antibodies against ovine CD4, CD8, and gamma delta T-cell receptor (TCR) markers. In all three sampl e groups, cells appeared to be non-randomly distributed throughout the lamina propria. Higher densities of lymphocytes were present in villu s than in crypt areas. CD8(+) cells were located principally around th e epithelial basement membrane, whereas CD4(+) cells were localised to wards the central villus area of the lamina propria. Lymphocytes beari ng the gamma delta T-cell receptor were more widely distributed, both in epithelial and lamina propria compartments. Ileum with tuberculoid lesions had higher densities of CD4 and gamma delta T-cell subsets whi le lepromatous lesions had lower densities of CD4 and CD8 cells compar ed with normal tissues. The median relative percentage of CD4(+) cells was increased and that of CD8(+) cells decreased in tuberculoid cases , with a corresponding increase in the CD4:CD8 ratio, while the relati ve percentage of gamma delta(+) cells was increased in lepromatous cas es.