Disease-dependent changes in T-cell populations in patients with shigellosis

In shigellosis, bacterial infection is associated with an extensive inflammation of the rectal mucosa, resulting in bloody dysentery. The role of T-cell-mediated pro-inflammatory mechanisms has been implicated in this process, but the specific role of T-cell subsets is still not well understood. In this study we attempted to identify the changes in T-cell populations in patients with shigellosis during the disease course. The T-cell subset distribution was analyzed by immunohistochemistry in the rectal mucosa and by immuno-flow cytometry in the peripheral blood. Blood and rectal biopsies were studied from patients with Shigella dysenteriae 1 (n= 11) and S. flexneri (n= 11) infection and 20 healthy age-matched controls. We found an expansion of gammadelta+T cells in the rectal mucosa, but a decrease in the percentage of gammadelta+T cells in the blood in acute shigellosis. There was also a preferential increase in CD8+ T cells in the surface epithelium of rectal tissue in patients infected with S. dysenteriae 1, but not in patients infected with S. flexneri. Our findings suggest that the rectal mucosal inflammation in shigellosis is associated with an expansion of T cells, in particular CD8+ and gammadelta+T-cell subsets in the gut mucosa, which may be of importance for the pathogenesis of shigellosis.