Large intestinal mast cell count and proteinase expression is associated with larval burden in cyathostomin-infected horses.

The research paper is about an investigation into the relationship between large intestinal mast cell counts and proteinase expression with the burden of cyathostomins, a parasitic nematode, in horses.

Research Objective and Methodology

• The main objective of the research was to investigate whether a relationship exists between mast cell (MC) populations, their proteinase expression, and the presence of the parasitic nematode, cyathostomins, in horses’ large intestine. The researchers also aimed to ascertain the predominant proteinase expressed. Interestingly, in other species, MC proteinases, particularly chymases, seem to have a protective role but there is limited knowledge about their function in equines.
• To establish this, the researchers first determined the cyathostomin count in the caecal (a pouch in the large intestine) of naturally infected horses (total 25) using two methods: luminal counts and pepsin digest for determining mural counts.
• MCs were identified and totalled in the caecal tissue by using a chemical called toluidine blue (TB). The expression of two types of proteinases, namely equine tryptase and the chymase equine mast cell proteinase-1 (eqMCP-1), in these cells was demonstrated using antibodies derived from rabbit labeled with fluorescent markers.

Research Findings and Conclusions

• A significant direct relationship was established between the MC counts and total cyathostomin burden and their representation in the luminal and mural sections. Similar direct relationships were also observed for MCs labeled with the two proteinases under examination and their total, luminal and mural cyathostomin counts.
• Moreover, the submucosa layer of the caecal tissue showed higher MC counts than the mucosa layer in all three labeling scenarios. This points to the likely location of these cells’ active involvement in dealing with the nematode infection.
• All caecal MC appeared to express the chymase proteinase with a small number also expressing tryptase in conjunction with chymase. This is indicative of the primary role likely played by chymase in driving the response to cyathostomin infection.
• The significant correlation between cyathostomin burden and mast cell counts along with the predominant expression of chymase establishes the relevance of this proteinase in equine immune response. Future research is recommended to investigate the dynamics of this proteinase expression, its potentially differential expression, and the exact role these MC proteinases play in the immune response to the cyathostomin infection.