Isospora suis (Apicomplexa: Coccidea) is the causative agent of neonatal porcine coccidiosis, a common parasitic infection of suckling piglets worldwide. I. suis replicates inside the epithelium of the small intestine and destroys the host cell during this process, leading to a sloughing of the epithelial lining. This results in heavy non-haemorrhagic diarrhoea and a reduced capacity of nutrient absorption by the mucosa, and therefore to reduced and uneven weaning weights of the piglets. Thus,

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... eonatal porcine coccidiosis is of considerable economic importance for pig production. Nevertheless, only very few data are available on the immune response to I. suis. The aim of this study was the characterisation of lymphocyte populations (T-cells and their subsets, natural killer cells, and B-cells) in blood, spleen, mesenteric lymph nodes (MLN) and the jejunal mucosa of infected piglets in comparison to healthy animals. First fundamental data about the involved cells of the immune system were obtained using a model of experimental infection of suckling piglets, multicolour flow cytometry of lymphocytes and immunohistochemistry of the gut mucosa. A significantly reduced frequency of T-cells, T-cell receptor-γδ+ (TcR-γδ+) cells, regulatory T cells and T-helper cells could be detected in blood, spleen and MLN of infected animals. B-cells showed an increase in the MLN, natural killer cells in the spleen. For cytotoxic T-lymphocytes (CTL) no difference could be detected between infected animals and controls. In the gut of infected piglets a strong and significant increase of T-cells, mainly caused by TcR- γδ+ cells, was observed. Furthermore, an experimental system for the functional characterisation of the immune response was established to identify antigen specific lymphocyte populations by in vitro restimulation. For this purpose ELISPOT-assays for the detection of IFN-γ production and proliferation assays were used as readout systems. Lymphocytes from blood and spleen showed an antigen-specific production of IFN-γ. Thi [...]