ARS | Publication request: Bovine WC1- gamma delta T-cells incubated with IL-15 express the natural cytotoxicity receptor CD335 (NKp46) and produce IFN-gamma in response to exogenous IL-12 and IL-18

Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2008
Publication Date: February 25, 2008
Citation: Johnson, W.C., Bastos, R.G., Davis, W.C., Goff, W.L. 2008. Bovine WC1- gamma delta T-cells incubated with IL-15 express the natural cytotoxicity receptor CD335 (NKp46) and produce IFN-gamma in response to exogenous IL-12 and IL-18. Developmental and Comparative Immunology. 32:1002-1010.

Interpretive Summary: The importance of the spleen in the immunity of cattle to blood parasites like Babesia bovis is well known, but the precise mechanisms involved are not fully understood. Recent studies have identified a number of cell populations within the spleen that work in concert to effect the demise of the invading pathogen. In this particular study, we describe a novel cell population that develops, proliferates and produces products involved in the demise of the invading parasite after stimulation with molecules that up-regulate the immune response.

Technical Abstract: The gamma delta T-cells of ruminants are believed to participate in innate immunity and have been described with regulatory and cytotoxic functions. Here we describe a subset of CD3+ TcRr1+ Wc1- CD8+ CD2+ gamma delta T-cells expressing CD335 (NKp46), classically associated with CD3- NK cells, as a consequence of incubation with IL-15. This population, undetectable at the time of collection, developed within 1 week of IL-15 culture from splenic leukocytes (SPL) reaching greater that 50% of the total gamma delta T-cells. However, they did not grow well from peripheral blood leukocytes (PBL). Splenic gamma delta T-cells positively selected by magnetic separation prior to incubation with IL-15 and analyzed by flow cytometry, consistently yielded CD3+ cells expressing CD335. These cells arose from the CD335- TcR1+ population suggesting that the new population represents up-regulation of CD335 by gamma delta T-cells. NKp46 mRNA expression from sorted IL-15-incubated SPL CD335+ TcR1+ or CD335+ TcR1- cells exceeded that of CD335_ TcR1+ cells. Incubation with IL-12 and IL-18 increased the numbers of CD335+ TcR1+ cells in both the PBL and SPL fractions as compared to controls or IL-12 or IL-18 alone. In addition, the CD335+ TcR1+ cell demonstrated a robust ability to produce IFN-gamma in response to exogenous IL-12 and IL-18. Taken as a whole, we describe a new phenotypically distinct bovine gamma delta T-cell subpopulation capable of participating in a type-1 immune response.