Mucosa‐associated lymphoid tissues as sites for uptake, carriage and excretion of tubercle bacilli and other pathogenic mycobacteria

Abstract

Summary Pathogenic mycobacteria, including those that cause tuberculosis and paratuberculosis, cross mucosal barriers by endocytosis within mucosal lymphoepithelial sites. These entry sites commonly include oropharyngeal and nasopharyngeal tonsils and Peyer's patches. Bacilli discharged at the basolateral surfaces of engulfing epithelial M cells are taken up by professional antigen-presenting cells associated with T lymphocytes of the parafollicular area. Dendritic cells and macrophages in these sites allow mycobacterial replication, due to the permissive immunological environment in lymphoepithelial tissues. Abrogation of local delayed-type hypersensitivity reactions generally ensures continuing integrity and function of these tissues. Phagocytes containing intracellular mycobacteria disseminate infection to other parts of the body and also probably migrate back onto the mucosal surface to shed bacilli.

Aerosol Exposure of White-Tailed Deer (Odocoileus Virginianus) to Mycobacterium Bovis

“…Interestingly, deer experimentally inoculated using the intratonsillar route routinely develop lesions in the medial retropharyngeal lymph nodes, suggesting an important role for the tonsils in natural infection (Palmer et al, 1999). The role of the tonsils in tuberculosis of other ruminant species has previously been highlighted (Lugton, 1999). A predilection for lesion development in the caudal lung lobes, similar to that seen in the present study, has previously been reported in whitetailed deer naturally or experimentally infected with M. bovis (Palmer et al, 1999;O'Brien et al, 2001).…”

Wild boar and red deer display high prevalences of tuberculosis-like lesions in Spain

“…In the red deer, prevalences may have been understimated according to Lugton [20] and Lugton et al [21], who suggest that up to one quarter of infected deer may show no detectable gross lesions. The use of a set of complementary techniques, particularly detailed inspection and culture of oropharyngeal tonsils should, in future studies, improve sensitivity allowing the detection of animals with early infections that do not present macroscopical lesions [20]. In conclusion, since it is impossible to quantify such bias in the prevalence estimates given here for both species, they must be considered as relative values.…”

“…Lymph nodes were dissected, sectioned serially and carefully examined for gross lesions. Inspection of the oropharyngeal tonsils (of special interest in deer [20]) could not be carried out in all of the sampled animals. Nevertheless, we expected that infection in the retropharyngeal lymphnodes would be highly correlated with that in the tonsils [29].…”

The innate immune response in human tuberculosis

“…It consists of (i) the epithelium, a layer of airway epithelial cells (AECs) forming a barrier that prevents invasion; (ii) the lamina propria, a layer of connective tissue and immune cells, including lymphocytes and macrophages; and (iii) a coating of a highly complex substance known as airway surface liquid (ASL), which contains mucus, immunoglobulin A and an array of other innate immune factors on the luminal surface. Also located in prime positions along the airways to encounter Mtb are bronchial‐ or nasal‐associated lymphoid tissues that are crucial for Mtb antigen sampling (Lugton, 1999). …”