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Title: The pathology and immunology of paratuberculosis in sheep and goats
Author: Little, D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Mycobacterium avium subspecies paratuberculosis (Map) infects macrophages and causes severe lesions of chronic granulomatous enteritis in sheep and other ruminants (Johne's disease). In this study, ovine paratuberculosis cases were examined histologically, and the presence of two distinct forms of intestinal pathology confirmed, characterised by either multibacillary lesions which exhibited a positive correlation with the presence of a marked macrophage infiltrate (lepromatous cases), or paucibacillary lesions which showed correlation with a cellular infiltrate which was lymphocytic in nature (tuberculoid cases). The presence of acid-fast bacteria was also found to correlate with evidence of serum antibody. Genomic DNA was extracted from the ileum of infected sheep and polymerase chain reaction (PCR) performed using IS900 primers to confirm Map infection. Immunoperoxidase staining of ileum demonstrated that the lymphocyte populations differed in density and relative percentages between both histological groups. The tuberculoid group had higher densities of CD4+, CD8+ and γδTCR+ subsets, and the lepromatous group lower densities of CD4+ and CD8+ subsets, when compared with control animals. Tuberculoid cases were associated with an increase in the relative percentage of CD4+ lymphocytes, whereas lepromatous cases had an increased relative percentage of γδTCR+ cells. Flow cytometry of lamina propria lymphocytes (LPL) isolated from the ileum of infected and control animals confirmed increased percentages of γδTCR+ cells in lepromatous cases than in controls, and higher percentages of CD8+ and γδTCR+ cells than in tuberculoid cases, which had correspondingly higher percentages of CD4+ cells. Higher percentages of γδTCR+ cells were also noted in mesenteric lymph node lymphocytes (MLNL) from lepromatous cases compared with control animals. Peripheral blood lymphocytes (PBL) of infected animals had increased percentages of B cells, and an associated increase in the percentage of MHC Class II positive cells compared with normal controls. The findings of this study suggest that ovine paratuberculosis is a disease with an immunological spectrum broadly comparable with that described for leprosy, with an apparent Thl like response in the tuberculoid form and a Th2 like response in the lepromatous form.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available