Cryptosporidiosis is a poorly controlled zoonosis caused by an intestinal parasite, Cryptosporidium parvum (Cp), with a high prevalence in ruminant farms. Young animals are particularly susceptible to this infection due to the immaturity of their intestinal immune system. In a neonatal mouse model, we demonstrated the importance of the innate immunity and in particular of CD11c+CD103+CD11b- dendritic cells (DC) in controlling the acute phase of Cp infection. During infection, in response to chemokine production by infected epithelial cells, newly recruited CD11c+CD103+CD11b- DC produce IL12 and IFNγ contributing to the parasite elimination process. According to the common classification of DC in different species (human, mouse, pig, sheep), this subpopulation can be identified as the cDC1 subset of conventional DC. The aim of this project is to better characterize intestinal DC subpopulations in lamb and calf at homeostasis and during Cp infection. The parasite invades and multiplies mainly in the ileum of animals. However, a peculiarity of young ruminants is the presence of a large ileal Peyer’s patch (lymphoid tissue) that extends all along the ileum. We therefore performed phenotypic and functional analyses of mononuclear phagocytes by flow cytometry and transcriptomic methods in various compartments of the small intestine. We characterized one population of macrophages and three subpopulations of DC. We demonstrated that the subset identified as cDC1 increases according to the age of animal, and this might be linked with the decrease in sensitivity to C. parvum observed with the age. We are currently investigating cDC1 subset during C. parvum infection.