Donor-specific cytotoxicity induced by allogeneic intestinal epithelial cells in a sponge matrix model

Small intestinal epithelial cells (IEC) constitutively express MHC class II molecules. However, little is known about the role of IEC in intestinal allograft rejection. The present study examined whether IEC can induce the development of cytotoxic T cells in vivo using a sponge matrix model. IEC isolated from ACI (RT1^a) rats were injected into polyurethane sponges implanted i.p. in Lewis (RT1¹) rats. Sponge grafts with ACI splenocytes or Lewis IEC were used as controls. The sponge grafts were removed and sponge-infiltrating cells (SIC) were harvested on post-operative days (POD) 7, 10, and 14. The phenotype of SIC was determined by FACS analysis and the cell-mediated cytotoxicity was measured using a chromium release assay. Non-specific inflammatory cells accumulated in the IEC sponge allografts during the first 10 days. By POD 14, however, 61% of SIC were T lymphocytes and 36% expressed cytotoxic T cell marker (OX-8). The cytotoxicity in IEC sponge allografts was detectable on POD 7 and POD 10, and markedly elevated on POD 14. The cytotoxicity induced by allogeneic splenocytes appeared in the sponge grafts on POD 7, peaked on POD 10, and declined thereafter. The allospecific cytotoxicity induced by IEC was dependent on host macrophages as pretreatment of animals with gadolinium, a rare earth metal that inactivates macrophages, abrogated the induction of cytotoxicity. We conclude that: (1) the migration and maturation of cytotoxic T cells can be induced in vivo by IEC and (2) IEC may contribute to the increased severity of intestinal rejection through interaction with macrophages.