RANTES (or regulated upon activation, normal T cell expressed and secreted) belongs to the rapidly growing chemokine family. It is mainly produced by T cells, epithelial cells, monocytes, fibroblasts, and mesanglial cells. Increased RANTES expression has been associated with a wide range of inflammatory disorders and pathologies. Mouse RANTES is the homolog molecule of human RANTES. The two have considerable homology in both sequence and structure. Using hRANTES as immunogen and the technique of rat B lymphocyte hybridoma, we raised two hybridoma cell lines secreting monoclonal antibodies (MAbs) to hRANTES, designated no. 1 and no. 2. Both MAbs can bind the hRANTES in FCM, Western blot analysis, and immunocytochemistry. No. 1 also worked well in immunohistochemistry of rat transplanted intestine, which may recognize the same epitope on human RANTES and rat RANTES. Thus, successful production of rat anti-human RANTES MAbs may provide a useful tool in further exploration of the biological function and pathological significance of RANTES and may provide a new method to judge early rejection after small bowel transplantation.