Immuno-histochemical study of ovine cystic echinococcosis (Echinococcus granulosus) shows predominant T cell infiltration in established cysts

•Established cysts of Echinococcus granulosus in sheep are associated with CD3+ T cells.•Most established cysts are in the lung.•Foxp3+ cells make up part of the local inflammatory infiltrate.

Ovine hydatidosis (OH; Echinococcus granulosus) is endemic in several European countries surrounding the Mediterranean basin. There have been a limited number of studies aimed at evaluating the local immune response to established tissue cysts in the ovine host. In the present study, immunohistochemical analysis of lymphocyte populations surrounding established cysts showed a predominance of CD3+ T cells compared to CD79+ B cells. A percentage of infiltrating lymphocytes were also FoxP3+, suggesting that established ovine cysts may be protected from immune aggression through the suppressive action of T regulatory cells. The present study contributes to the understanding of local immune responses to ovine echinococcosis.