Localization of alpha/beta and gamma/delta 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 alpha/beta T cells, both CD4(+) (150%) and CD8(+) (60%), and of gamma/delta 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 alpha/beta T cells, The number of CD4(+) T cells within the Peyer's patch of the ileum increased dramatically; however, there a-as 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 he 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.