Localization of α/β and γ/δ T lymphocytes in Cryptosporidium parvum- infected tissues in naive and immune calves

The nature of the host's T-lymphocyte population within the intestinal villi following Cryptosporidium parvum infection was characterized with a bovine model of cryptosporidiosis. In naive animals, infection with C. parvum resulted in substantial increases in the numbers of α/β T cells, both CD4⁺ (150%) and CD8⁺ (60%), and of γ/δ T cells (70%) present within the intestinal villi of the infected ileum. In immune animals, the host T- lymphocyte response to a challenge infection with C. parvum was restricted to α/β T cells. The number of CD4⁺ T cells within the Peyer's patch of the ileum increased dramatically; however, there was little change in the number or localization of CD4⁺ T cells within the intestinal villi. In contrast, the number of CD8⁺ T cells within the intestinal villi increased following a challenge infection. In addition, the CD8⁺ T cells were found to be intimately associated with the epithelial cells of the intestinal villi. The precise correlation between the accumulation of CD8⁺ T cells and the normal site of parasite development suggests an important role for CD8⁺ T cells in the immune animal.