Under additive genetic models, CD28-rs3116494 (OR = 1.29 [95% CI 1.11, 1.51], P = 0.0011) and CD80-rs3850890 (OR = 1.16 [95% CI 1.02, 1.31], P = 0.0283) were associated with DKD susceptibility adjusted for age, gender, body mass index (BMI), duration of diabetes, and HbA1c. Here, CD80 is linked to diabetes mellitus.