This study investigated the role of pre and posttransplant natural immunoglobulin G antibodies (Nabs) reactive to varied antigenic structures, including apoptotic cells to allograft outcome. This is a retrospective, multicenter study including 980 kidney transplant recipients across 4 centers. Baseline sera for 714 of 980 patients were collected at the time of transplant or within 7 d before transplantation, whereas baseline sera for 204 of 980 patients were collected between 7 d to 1 mo before transplantation. Elevated pretransplant Nabs were associated with graft loss (hazard ratio [HR] 2.71; 95% confidence interval [CI], 1.15-6.39; P  =  0.0232), the composite endpoint of graft loss or severe graft dysfunction (HR 2.40; 95% CI, 1.13-5.10; P = 0.0232), and T cell–mediated rejection (odds ratio [OR] 1.77; 95% CI, 1.07-3.02; P = 0.0310). In patients with high pretransplant Nabs, the subsequent development of posttransplant Nabs was associated with both T cell–mediated rejection (OR 3.64; 95% CI, 1.61-8.36; P = 0.0021) and mixed rejection (OR 3.10; 95% CI, 1.02-9.75; P = 0.0473). Finally, elevated pre- and posttransplant Nabs combined with DSAs were associated with increased risk of composite outcomes (HR 3.97; 95% CI, 1.51-10.43; P = 0.0052) and T cell–mediated rejection (OR 7.28; 95% CI, 2.16-25.96; P = 0.0016).

This study investigated the relationship between the pretransplant fasting C-peptide level and posttransplant graft function and failure among T2DM patients who have undergone simultaneous pancreas and kidney (SPK) transplants. Patients were categorized into 3 groups: low (≤2 ng/mL), medium (>2–8 ng/mL), and high (>8 ng/mL). There were a total of 76 SPK recipients (low, n = 14; medium, n = 47; high, n = 15). A total of 16 recipients reached the composite outcome of uncensored graft failure (n = 8) or need for anti-diabetic agents (n = 8) posttransplant. None of the recipients in the low C-peptide group reached the composite outcome endpoint, whereas 11 (23.4%) (including 6 uncensored graft failures) in the medium group and 5 (33.3%) (including 2 uncensored) in the high group reached the composite outcome. In a fully adjusted model, each pretransplant C-peptide unit was not associated with an increased risk of the composite outcome, GF, or death-censored composite outcomes. However, in multivariate analysis with limited adjustment, pretransplant C-peptide was associated with the composite outcome (hazard ratio: 1.18, 95% confidence interval, 1.01-1.38; P = 0.03) and death-censored composite outcome (hazard ratio: 1.20; 95% confidence interval, 1.01-1.42; P = 0.03). Although the small sample size, higher levels of pretransplant C-peptide may be associated with inferior posttransplant outcomes that include graft dysfunction.