Discussion

 There is increasing interest in tuft cells due to their proposed function in sensing environmental changes in the gut lumen, and in initiating the Type 2 T helper (Th2) immune response to gastro-intestinal parasite infections in mice. Specific tuft cell markers have been identified and have demonstrated the expansion of tuft cells over the course of an infection, as part of a ‘feed-forward loop’ with Group 2 Innate Lymphoid Cells (ILC2). The aim of this project was to determine whether murine tuft cell markers were also expressed in the abomasum epithelium of sheep and if so, whether an expansion of the cells expressing these markers was observed during infection with the ovine gastro-intestinal nematode Teladorsagia circumcinta.Antibodies to the murine tuft cell markers POU2F3, Gfi1b, DCLK-1 and TRPM5 were evaluated using immunohistochemistry techniques on ovine tissues. Anti-POU2F3 and anti-Gfi1b were found to give a strong specific signal on putative tuft cells throughout the gastro-intestinal tract. The percentages of POU2F3+ epithelial cells in the ovine abomasum over the course of a T. circumcinta infection showed similar increases to those seen in the mouse, suggesting that the POU2F3+ cells in the ovine abomasum are tuft cells. In addition, we have identified a high number of POU2F3+ cells in abomasal epithelium tissue of sheep infected with the related nematode Haemonchus contortus. Further investigations are underway to assess the specificity of anti-DCLK-1 and anti-TRPM5 for putative ovine tuft cells, and to determine whether all putative ovine tuft cells express the same markers. This project has taken the first steps in identifying markers of ovine tuft cells, enabling further investigation of the importance of these cells in the ovine Th2 response to parasitic nematode infections.