Abstract Objectives: Allograft rejection is an important cause of early and long-term graft loss in kidney transplant recipients. Tumor necrosis factor-alpha promotes T-cell activation, the key reaction leading to allograft rejection. Here, we investigated whether serum and urinary tumor necrosis factor-alpha levels can predict allograft rejection. Materials and Methods: This study included 65 living related-donor renal transplant recipients with mean follow-up of 26 ± 9 months. Serum and urinary tumor necrosis factor-alpha levels were measured at pretransplant and at posttransplant time points (days 1 and 7 and months 3 and 6); serum creatinine levels were also monitored during posttransplant follow-up. Standard enzyme-linked immunoabsorbent assay was used to detect tumor necrosis factor-alpha levels. Clinical variables were monitored. Results: Nine of 65 patients (13.8%) had biopsy-proven rejection during follow-up. Preoperative serum and urinary tumor necrosis factor-alpha levels were not significantly different when we compared patients with and without rejection. Serum tumor necrosis factor-alpha levels (in pg/mL) were significantly higher in the allograft rejection versus nonrejection group at day 7 (11.5 ± 4.7 vs 15.4 ± 5.8; P = .029) and month 1 (11.1 ± 4.8 vs 17.8 ± 10.9; P =.003). Urinary tumor necrosis factor-alpha levels (in pg/mL) were also elevated in the allograft rejection versus the nonrejection group at days 1 (10.2 ± 2.5 vs 14.1 ± 6.8; P = .002) and 7 (9.8 ± 2.2 vs 14.5 ± 2.7; P < .001) and at months 1 (8.0 ± 1.7 vs 11.8 ± 2.4; P < .001), 3 (7.7 ± 1.6 vs 9.6 ± 1.7; P = .002), and 6 (7.4 ± 1.6 vs 8.9 ± 0.9; P = .005). Conclusions: Our preliminary findings suggest that tumor necrosis factor-alpha has a role in diagnosing renal transplant rejection. Serum and urinary tumor necrosis factor-alpha levels may be a possible predictor for allograft rejection. Key words: -6>8(;<?2 :=/> :??5>;8<2 ;0<?6 >:=<749=<>=>;8< Introduction Renal transplant is the best treatment for end-stage renal disease. Acute rejection is one of the most important causes of allograft dysfunction and can lead to early and long-term graft loss in kidney transplant recipients despite antirejection therapy. 1 Younger recipients, older donors, donor-recipient human leukocyte antigen (HLA) mismatches, pretransplant anti-HLA antibodies, panel reactive antibodies, and the adequacy of baseline immuno- suppression are major predictors of acute rejection. 2 Transplant renal biopsy is the criterion standard for diagnosing acute rejection and guiding corrective therapy; however, many centers do not routinely consider graft biopsy at the onset of renal dysfunction. 3 A noninvasive test would be beneficial for diagnosing acute renal rejection. Tumor necrosis factor-alpha (TNF-) is a proinflammatory cytokine produced by monocytes/- macrophages that binds to TNF receptors on endothelial or tubular cells. Tumor necrosis factor- alpha activates lymphocytes and antigen-presenting cells and increases expression of the MHC class II genes and intercellular adhesion molecules on the cell surface, which causes cells to undergo apoptosis. 4 The role of TNF- in allograft rejection has been previously well defined, with animal studies also showing the important role of TNF- in ischemia-reperfusion injury progression. 5 However, &(,) '*+) +,*(%,) (,+)* ,+ (* !"" ,)% *%*(* Serum and Urinary Levels of Tumor Necrosis Factor-Alpha in Renal Transplant Patients !=6:;6? $?<>3:( -;/>5;2 * :89 ?1;:2 # ?9>?1 $=:=< =:=0?<;2 )?=> )?/;(2 !=9;9 =;5;2 # &71?> =<?2 =>1= $=:=< "32 * ;9; 60;<2 * 60;< )3:(1?< # :81 >.? * ?4=:>1?<> 8/ ?0;5=9 ;898"62 >.? # ;;7;8< 8/ ?4.:898"62 ?4=:>1?<> 8/ &<>?:<=9 ?0;5;<?2 >.? ?4=:>1?<> 8/ <?7>.?7;=2 =<0 >.? ?4=:>1?<> 8/ :898"62 &7>=<%39 =539>6 8/ ?0;5;<?2 &7>=<%39 <;?:7;>62 &7>=<%392 )3:(?6 !+&"***+)%$ ).;7 7>306 =7 4:?7?<>?0 =7 487>?: 4:?7?<>=>;8< => >.? *7> 3:84?=< &113<8"?<?>;5 =<0 !;7>85814=>;%;9;>6 -8</?:?<5? ).? 7>306 =7 73448:>?0 %6 >.? $5;?<>;/;5 ?7?=:5. ,:8?5>7 -88:0;<=>;8< <;> , 8/ &7>=<%39 <;?:7;>6 ;>. 4:8?5> <31%?: ' ).? =3>.8:7 .=? <8 58</9;5>7 8/ ;<>?:?7> >8 0?59=:? &((*%&+,+ ')&($ !=6:;6? $?<>3:( -;/>5;2 ?4=:>1?<> 8/ ?0;5=9 ;898"62 &7>=<%39 ?0;5=9 =539>62 &7>=<%39 <;?:7;>62 -=4=2 =>;.2 &7>=<%392 )3:(?6 &+*$ # *+ '+ ',"$ .=6:;6?7?<>3:("1=;9581 *(,*+)'" '+ ",+,'" ('+%"'+)'),&+ $ #'$## "