Intragraft cytokine and T cell receptor gene expression was analyzed in rejecting renal allografts by polymerase chain reaction (PCR). Message for IL-1 beta, IL-6, and TNF-alpha was detected in nephrectomy tissue with pathological evidence of acute or chronic rejection. Similarly, mRNA for both IL-6 and TNF-alpha was present in renal biopsies from acute rejecting kidneys. IL-2R, IL-4, and IL-5 mRNA was present in both rejecting and rejected kidney allografts, indicating that these cytokines may play a role in ongoing renal allograft rejection. Conversely, IL-2, IL-7, and IFN-gamma message was detected infrequently. In order to address the diversity of T cells in rejecting kidneys, we have analyzed the clonality of the TcR present within the allograft tissue. Rearranged TcR genes were identified in all allografts examined (n = 16) indicating the presence of T cells bearing the alpha/beta TcR. We have determined that there is a heterogeneous infiltration of T cells in the rejected allograft with TcR representing x = 7.47 +/- 2.4 families rearranged in samples obtained from nephrectomies, whereas x = 5.33 +/- 0.58 families were detected in samples obtained from biopsy tissue. These data indicate that (1) cytokines are produced locally which may contribute to graft cell destruction, (2) the heterogeneity of intragraft T cells during kidney allograft rejection may exist because nonspecific lymphocytes have been recruited to the site by locally produced cytokines or because T cells are responding to multiple epitopes or multiple donor antigens. Detection of intragraft cytokines and TcR may prove useful in elucidating the mechanism of rejection and therefore lead to improved immunosuppression.