Immunohistochemical study and mRNA cytokine profile of the local immune response in cattle naturally infected with Calicophoron daubneyi.

In order to recognize the local immune response of the definitive host to Calicophoron daubneyi natural infection, an immunohistochemical study was carried out in the reticulum and rumen in 49 naturally infected cattle. The role of cytokines (IL-4 and IL-10 interleukins and IFN-γ) in the activation of specific defence mechanisms was evaluated by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) assays to study cytokine mRNA expression. In all infected animals, CD3+ T lymphocytes seemed to be the main element of the inflammatory infiltrate in the reticular and ruminal lamina propria at the point of the parasite adhesion. Intraepithelial globule leukocytes also showed immunolabelling for CD3. Most CD3+ cells also expressed CD4 (T cell helper) antigen although sporadic CD8+-cytotoxic lymphocytes were observed. Local expression of IFN-γ was observed in damaged papillae at the site of parasite attachment and in scattered cells in the lamina propria. B cells (CD79αcy+, CD45+ and IgG+) were found constantly in relation to lymphoid aggregates. MAC387 was expressed in squamous epithelium and in macrophages of the lamina propria of affected papillae. Macrophages in this location also stained positively for CD163 and CD68. Intraepithelial Langerhans cells and macrophages located in the lamina propria showed immunopositivity for MHCII in the affected areas. RT-qPCR analysis confirmed a statistical significant increase of IFN-γ, and IL-10 expression (p<0.01) in the rumen associated with the presence of flukes. These findings suggest a predominant Th1 polarized local immune response with the probable involvement of Th regulatory cells in cattle C. daubneyi natural infection.

Pathological changes in cattle naturally infected by Calicophoron daubneyi adult flukes.

Local host response and parasite distribution were studied in the forestomachs, abomasum, duodenum and regional lymph nodes of cattle suffering from bovine paramphistomosis. The parasites were found attached, by its ventral sucker, to small conical papillae of the rumen and reticulum. Affected papillae, showed morphological changes denoted by very narrow stalks and expanded heads. Histologically, these changes were characterized by epithelial acanthosis-hyperkeratosis of the epithelium. Infiltration of inflammatory cells was often related with the epithelial changes, although it was also found in the duodenal mucosa and submucosa. These cells were arranged as aggregates or follicles but sparse infiltration of eosinophils, globule leukocytes, mast cells or macrophages was also observed in the lamina propria. Tissue damage and inflammatory reaction were more severe in the ruminal atrium, where the largest number of flukes and affected papillae were observed. In contrast, lesions in the ruminal dorsal sac were absent or mild. Statistical correlation between lesion severity and parasite burden was confirmed.