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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Infectious Bacterial Diseases Research » Research » Publications at this Location » Publication #333202

Title: Measuring bovine gamma delta T cell function at the site of Mycobacterium bovis infection

item RUSK, RACHEL - Kansas State University
item Palmer, Mitchell
item Waters, Wade
item MCGILL, JODI - Kansas State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/27/2016
Publication Date: 12/5/2016
Citation: Rusk, R.A., Palmer, M.V., Waters, W.R., Mcgill, J.L. 2016. Measuring bovine gamma delta T cell function at the site of Mycobacterium bovis infection. Meeting Abstract. 193-194:38-49. doi: 10.1016/j.vetimm.2017.10.004.

Interpretive Summary:

Technical Abstract: The causative agent of tuberculosis (TB) in cattle is Mycobacterium bovis. The characteristic lesions of bovine TB are well-organized pulmonary granulomas. Gamma delta T cells are a unique subset of nonconventional T cells that play major roles in both the innate and adaptive arms of the immune system. Bovine gamma delta T cells have the capacity for multiple immune functions during infection with M. bovis; however, specific gamma delta T cell responses in vivo at the site of M. bovis remain unclear. To identify novel functions for gamma delta T cells in response to M. bovis infections, RNA sequencing and transcriptomics analysis was completed on peripheral blood gamma delta T cells isolated from virulent M. bovis infected or M. bovis Bacillus Calmette–Guérin (BCG) vaccinated cattle. Differentially expressed genes were then confirmed with real-time PCR. In an attempt to model in vivo cell-to-cell interactions at the site of infection, gamma delta T cells were also isolated from BCG vaccinated calves and co-cultured with autologous, BCG infected, macrophages. Gamma delta T cell chemokine and cytokine expression was analyzed via ELISA and real-time PCR. To determine the relevance of our RNA-sequencing and in vitro co-culture results to in vivo infection, tissue samples of granulomatous lesions from the lungs and mediastinal lymph nodes of virulent M. bovis infected cattle were collected 3 months after infection. mRNA transcripts for gamma delta T cell expression of IFN-gamma, IL-17, IL-10, and CCL2 were microscopically evaluated within the granulomas using an in situ hybridization system, RNAScope (Advanced Cell Diagnostics Inc.). Co-culture experiments and transcriptomics analysis revealed increased expression of chemokines by gamma delta T cells responding to M. bovis infection. The novel ISH assay revealed that cytokine expression by the gamma delta T cells varied within the lesions, with low expression of IFN-gamma, IL-10, or IL-17 by gamma delta T cells in situ at this time-point after infection. Interestingly, gamma delta T cells expressed significant levels of CCL2 within late-stage granulomas and during initial in vitro interactions with BCG infected macrophages. Our results suggest that gamma delta T cells accumulate within the granulomas, and may contribute to the anti-mycobacterial host immune response.