Interleukin 18 (IL-18) upregulation in acute rejection of kidney allograft

Interleukin 18 (IL-18) is a potent proinflammatory cytokine involved in the host defence by upregulating both innate and acquired immune responses and may be of particular importance also in mechanisms of kidney allograft rejection. Immunohistochemical staining of protocol biopsies showed constitutive IL-18 expression in the epithelium of distal tubules with the induction of immunoreactivity in acute rejection patients where also proximal tubules, infiltrating leukocytes, and endothelium were strongly positive. Furthermore, serum levels of IL-18 were significantly elevated in patients with acute rejection of kidney allograft (1247+/-389 pg/l) as compared to patients with uncomplicated outcome of kidney transplantation (444+/-164 pg/l) and subjects with acute tubulointerstitial nephropathy (385+/-155 pg/l, p<0.0001 for both comparisons). Tissue culture model of renal epithelial cells expressed IL-18 mRNA constitutively and released mature IL-18 in response to TNF-alpha and IFN-gamma. We assume that upregulation of epithelial IL-18 plays an important role in immune and immunopathological reactions in renal parenchyma and contributes to rejection mechanisms of kidney allograft.