ACTIVATION OF INTESTINAL INTRAEPITHELIAL T-LYMPHOCYTES IN CALVES INFECTED WITH CRYPTOSPORIDIUM-PARVUM

The objective of this study was to identify disease-related changes in lymphocyte populations within ileal mucosae of carves with cryptospor idiosis, Groups of five neonatal calves were orally infected at 3 days of age with 10(8) oocysts and maintained in enteric-pathogen-free con ditions until clinical disease was established or until the animals ha d recovered from disease. Age-matched uninfected calves were used for comparison, Ileal mucosal lymphocytes were collected, quantitated, and phenotyped to determine whether changes in lymphocyte composition occ urred in infected animals, We observed significantly larger numbers of intraepithelial CD8(+) T lymphocytes in ileal mucosae from acutely in fected calves compared with those from control animals, In addition, a proportion of intraepithelial CD4(+) T cells from acutely infected ca lves coexpressed CD25, whereas there was an absence of coexpressed CD2 5 on CD4(+) T cells from control calves, Ex vivo reverse transcriptase PCR of RNA from intraepithelial lymphocytes from control calves showe d a cytokine expression pattern consisting of tumor necrosis factor al pha (TNF-alpha) and gamma interferon (IFN-gamma), while intraepithelia l lymphocytes from calves with cryptosporidiosis expressed IFN-gamma b ut not TNF-alpha, Together, the results indicate that changes occur in the ileal intraepithelial lymphocyte population coincidently with Cry ptosporidium parvum-induced enteric disease.