Introduction: Immunoglobulin G (IgG) is the most distributed subclass of immunoglobulin in the human body. It is a major component of humoral immunity and plays an important role in biological reactions such as protection from infection or attack of foreign body. After kidney transplantation, it is important to adjust immunosuppressive therapy to avoid allograft rejection or opportunistic infection for the maintenance of stable graft function and patient survival. Although optimal protocol of immunosuppressive therapy is being constantly modified in each transplant center, there is no clinically applicable and easy-to-use parameter to determine the optimal immunosuppressive therapy. In this study, we investigated the clinical significance of IgG, and evaluate the potential of IgG as an indicator of optimal immunosuppressive therapy and post-transplant complications in kidney transplant recipients at our institute.
Method: In the study, we retrospectively collected and analyzed the data of 122 patients with end-stage renal disease, who underwent kidney transplantation in Nagasaki University Hospital. The age of subjects was 56.6±14.4 years old, and the period of follow-up was 12.2±9.4 years. The cases of combined kidney transplantation, such as simultaneous pancreas-kidney and liver-kidney transplantation were excluded. Total IgG level of the subjects was measured, and the association of IgG level with patient characteristics, contents of immunosuppressive therapy, and post-transplant complications were comprehensively and statistically analyzed.
Results: IgG level of the subjects was 957±267 mg/dl. In patient background, it was significantly lower in female than in male, and negatively correlated with donor age at transplantation and allograft function. In analysis of immunosuppressive therapy, patients taking mycophenolate mofetil (MMF) had significantly lower IgG level than those not taking. Interestingly, the positive test of CMV-PCR and history of COVID-19 were significantly associated with lower IgG level.
Conclusion: IgG level of kidney transplant recipients was associated with specific patient character, type of immunosuppressive agent, and post-transplant complications. Measurement and evaluation of IgG level after kidney transplantation may contribute to optimizing immunosuppressive therapy and predicting the occurrence of post-transplant complications.