Intestinal and hepatic recruitment of alloreactive effector cells after transfer of in vivo primed alloreactive T cells into conditioned secondary allogeneic recipients irrespective of the original priming site. (A) Primary and secondary Balb/c (H-2^d) recipients were conditioned (2 × 4 gy) and received transplants of either luc⁺ or wild-type allogeneic FVB/N (H-2^b) T cells, respectively, to simulate comparable conditions in both groups. On day 3, luc⁺ T cells were isolated from either pLN (cLN and iLN combined) or mLN, or spleen. Subsequently, these in vivo primed alloreactive donor T cells were injected separately into secondary recipients to track their in vivo short-term homing. (B) Within 18 hours after secondary transfer, luc⁺ T cells predominantly homed to abdominal sites in all of the analyzed groups (1 of 5 representative experiments is shown). (C) Ex vivo imaging confirmed that alloreactive luc⁺ donor cells homed to the gastrointestinal tract (GIT), the liver (above GIT), and the spleen (right from GIT) in conditioned secondary recipients irrespective whether in vivo priming occurred in pLN, mLN, or spleen.