Probes for TGF-β

In the present study, we evaluated expression of IFN-γ, IL-17, TNF-α, IL-10 and TGF-β by mucosal cells, including WC1+ γδ T cells, in ileal tissues taken from non-infected cattle and cattle naturally infected with Mycobacterium avium subsp paratuberculosis (MAP). Infected cattle were either in the subclinical or clinical stage of infection. We hypothesized that the cytokine profile of the WC1+ γδ T cell subset would be different between subclinical and clinical cattle. Our data indicate a significant increase in the numbers of WC1+ γδ T cells expressing IL-10 in clinical cattle compared to subclinical and non-infected cattle. We observed a significant increase in TGF-β expression by non-WC1+ cells in clinically infected cattle. Expression of IFN-γ, IL-17 and TNF-α in mucosal cells, including the WC1+ γδ T cell subset, was identified in all examined groups. However, our data indicate that the stage of infection did not significantly influence expression of these proinflammatory cytokines. This study demonstrates changes in the cytokine mRNA expression profile of mucosal cells in the ileum, and specifically WC1+ γδ T cells, as cattle progress to the clinical disease. The change is characterized by an increase in expression of anti-inflammatory cytokines.

The hallmark lesion of tuberculosis in humans and animals is the granuloma. The granuloma represents a distinct host cellular immune response composed of epithelioid macrophages, lymphocytes, and multinucleated giant cells, often surrounding a caseous necrotic core. Within the granuloma, host-pathogen interactions determine disease outcome. Factors within the granulomas such as cytokines and chemokines drive cell recruitment, activity, function and ultimately the success or failure of the host's ability to control infection. Hence, an understanding of the granuloma-level cytokine response is necessary to understand tuberculosis pathogenesis. In-situ cytokine expression patterns were measured using a novel in situ hybridization assay, known as RNAScope^® in granulomas of the lungs, tracheobronchial lymph nodes and caudal mediastinal lymph nodes of cattle experimentally infected with Mycobacterium bovis via aerosol exposure. In spite of microscopic morphological similarities, significant differences were seen between late stage granulomas of the lung compared to those of the tracheobronchial lymph nodes for IL-17A, IFN-γ, TGF-β, IL10 and IL-22 but not for TNF-α. Additionally, significant differences were noted between granulomas from two different thoracic lymph nodes that both receive afferent lymphatics from the lungs (i.e., tracheobronchial and caudal mediastinal lymph nodes) for TNF-α, IL-17A, IFN-γ, TGF-β and IL-10 but not for IL-22. These findings show that granuloma morphology alone is not a reliable indicator of granuloma function as granulomas of similar morphologies can have disparate cytokine expression patterns. Moreover, anatomically distinct lymph nodes (tracheobronchial vs caudal mediastinal) differ in cytokine expression patterns even when both receive afferent lymphatics from a lung containing tuberculoid granulomas. These findings show that selection of tissue and anatomic location are critical factors in assessing host immune response to M. bovis and should be considered carefully.

Regardless of host, pathogenic mycobacteria of the Mycobacterium tuberculosiscomplex such as Mycobacterium bovis, induce a characteristic lesion known as agranuloma, tubercle or tuberculoid granuloma. Granulomas represent a distinct host response to chronic antigenic stimuli, such as foreign bodies, certain bacterial components, or persistent pathogens such as M. bovis. Granulomas are composed of specific cell types including epithelioid macrophages, lymphocytes and a morphologically distinctive cell type, the multinucleated giant cell. Multinucleated giant cells are formed by the fusion of multiple macrophages; however, their function remains unclear. In humans, giant cells in tuberculous granulomas have been shown to express various cytokines, chemokines and enzymes important to the formation and maintenance of the granuloma. The objective of this study was to quantitatively assess multinucleated giant cell cytokine expression in bovine tuberculoid granulomas; focusing on cytokines of suspected relevance to bovine tuberculosis. Using calves experimentally infected with M. bovis, in situ cytokine expression was quantitatively assessed using RNAScope^® for the following cytokines TNF-α, IFN-γ, TGF-β, IL-17A and IL-10. Multinucleated giant cells in bovine tuberculoid granulomas expressed all examined cytokines to varying degrees, with differential expression of TGF-β, IL-17A and IL-10 in giant cells from early versus late stage granulomas. There was a modest, positive correlation between the level of cytokine expression and cell size or number of nuclei. These results suggest that multinucleated giant cells are active participants within bovine tuberculoid granulomas, contributing to the cytokine milieu necessary to form and maintain granulomas.