Interleukin-12 mRNA levels in renal allograft fine-needle aspirates do not correlate with acute transplant rejection.

TH1 cytokines, including gamma-interferon (IFN), are critical in the initiation and progression of allograft rejection. As interleukin (IL)-12 up-regulates gamma-IFN, we assessed the role of IL-12 in human transplant rejection. Twenty renal allograft fine-needle aspirates from 19 patients were obtained, evaluated in the standard fashion, and assessed for gamma-IFN and IL-12p40 subunit mRNA levels using nested reverse transcriptase polymerase chain reaction. Ten aspirates demonstrated acute rejection by clinical criteria, and 9 of the 10 aspirates contained gamma-IFN while only 3 demonstrated IL-12; there were no distinguishing characteristics for these 3 patients with regard to therapy, or time of onset and severity of rejection. Seven patients without clinical or morphologic rejection failed to demonstrate gamma-IFN or IL-12. Three patients had discrepant findings; there was no morphologic rejection, yet all 3 patients contained gamma-IFN and 1 patient demonstrated rejection on subsequent biopsy. However, only 1 aspirate exhibited IL-12 and this patient had no documented subsequent rejection. This study confirms the association of gamma-IFN mRNA with acute rejection. In contrast, IL-12 mRNA does not appear to play a key role early in the rejection process.