Cytotoxic T cells in AIDS colonic cryptosporidiosis

Background/Aims-It is not known how enteric cryptosporidiosis induces sever e intestinal impairment despite minimal invasion by the parasite. The aim o f this study was to analyse the histological features and locally implicate d immune cells in colonic biopsies of AIDS related cryptosporidiosis. Patients/Methods-Colonic biopsies from patients with AIDS related cryptospo ridiosis (n = 10, group I), patients with AIDS but without intestinal infec tion (n = 9, group II), and human seronegative controls (n = 9, group III) were studied. Using immunohistochemistry the infiltrating mononuclear cells were analysed in both the epithelium and lamina propria for the expression of CD3, CD8, TiAl, granzyme B, and CD68 and for glandular expression of hu man major histocompatibility complex DR antigen (HLA-DR). Results-Severe histological changes, resulting in abundant crypt epithelial apoptosis and inflammatory infiltrate in the lamina propria, were seen in all biopsies from group I. A significant increase of CD8+, TiAl+, and granz yme B+ T cells in the lamina propria and HLA-DR glandular expression was no ted in group I compared with groups II and III. However, the number of intr aepithelial lymphocytes, lamina propria CD3+ T cells, and macrophages was n ot significantly increased in cryptosporidiosis specimens compared with con trols. Conclusion-Epithelial apoptosis mediated by granzyme B+ cytotoxic host T ce lls might play a major role in the development of colonic lesions in AIDS r elated cryptosporidiosis.