In vivo and in vitro models of intestinal intraepithelial lymphocyte development
Intestinal intraepithelial lymphocytes (IELs) make up a vast, but poorly understood population of lymphocytes. Located between epithelial cells that line the gut, they may provide a first line of defense against invading pathogens. Intriguingly, the largest population of IELs, TCRγδ+CD8αα + T cells, appears to be extrathymically derived. A more complete understanding of the origin of these cells may lead to a better understanding of their function. We, therefore, have utilized both in vivo and in vitro experimental systems to investigate IEL development. In vivo, the absence of IL-2, in IL-2 deficient (IL-2−/− ) mice, leads to reduced TCRγδ+CD8αα + IELs. Additionally, this reduction in TCRγδ+ IELs is not secondary to the colitis seen in IL-2−/− mice, as it is also present in gnotobiotic IL-2−/− mice. Furthermore, hematopoietic progenitor cells from IL-2 −/− bone marrow have an intrinsic defect in their ability to regenerate TCRγδ+ IELs after transfer to irradiated, CD45 congenic recipients. IL-2, therefore, appears to play an important role in IEL development. Given the limitations of using in vivo systems to dissect IEL development, in addition to the possibility that intestinal epithelial cells may play a key role in promoting IEL development, we have developed an in vitro model. A culture system has been developed in which freshly isolated small intestinal epithelial cells are cultured with hematopoietic progenitor enriched bone marrow cells. Preliminary experiments reveal that after 30 days of co-culture clusters of cells can be seen in close contact with the epithelial cell layer. These clusters appear to be negative for the expression of such lymphoid specific genes as RAG, Ets-1, AIOLOS and GATA-3. After relocation of the laboratory to the United Kingdom, primary IEC cultures were not re-established. Further experimentation needs to be conducted in order to confirm that IEC can support IEL development. The in vitro model system will provide a useful tool for further study of IEL development.
Contractor, Nikhat Vaseem, "In vivo and in vitro models of intestinal intraepithelial lymphocyte development" (2001). Dissertations available from ProQuest. AAI3031653.