Kinetics of intestinal intraepithelial lymphocytes during acute graft‐versus‐host disease in mice

We examined the kinetics of intestinal intraepithelial lymphocytes (IEL) and the incidence of apoptosis at villus or crypt sites during the development of non‐irradiated acute graft‐versus‐host disease (GVHD). The first IEL to increase were host‐origin on day 3 and the donor‐derived IEL appeared first on day 12 after GVHD induction. Unique CD3⁺CD4⁺CD8α/α⁺ IEL were significantly increased on day 6 and an appreciable number of IEL bearing T cell receptor Vβ capable of recognizing self‐superantigen were detected on day 9. The sudden appearance of apoptosis and reduction of mitotic activity occurred on day 12, accompanied by a dramatic decrease of CD3⁺CD4⁻CD8α/α⁺ IEL of host origin. CD8α/α⁺ IEL of host origin, which expand and then decrease by apoptosis at the early stage of acute GVHD, may be associated with pathogenesis of the enteropathy occurring during acute GVHD.