B-117 Inverse Association Between Regulatory T and B Cells with HLA antibodies and Donor-specific Antibodies in Kidney Transplantation

Abstract Background Regulatory T cells (Tregs) and regulatory B cells (Bregs) were critical in maintaining immune tolerance. However, the relationships with Human Leukocyte antigen (HLA) antibody levels in kidney transplant recipients are not well understood. This study aimed to investigate the association between Treg and Breg and HLA antibodies in kidney transplantation. Methods Peripheral blood was collected from 41 kidney transplant recipients. Tregs were quantified by flow cytometry using CD3+CD4+CD25+CD127- markers, while Bregs were identified by CD3-CD19+CD24+CD27+CD38+ markers. HLA antibodies and donor-specific antibodies (DSA) were measured using a Luminex-based solid-phase immunoassay. Patients were divided into two subtypes: 1) HLA-positive vs. HLA-negative, and 2) DSA-positive vs. DSA-negative. Data normality was assessed using the Shapiro-Wilk test, and differences between groups were evaluated using the Mann-Whitney U test. Spearman correlation was analyzed in the relationship between regulatory cells and antibody levels. Results The HLA-positive group had significantly lower median Treg levels compared to the HLA-negative group (1.38 vs. 6.16 ×103/µL, p = 0.04). Similarly, the DSA-positive group had significantly lower median Breg levels compared to the DSA-negative group (0.05 vs. 1.98×103/µL, p = 0.001). Treg levels were inversely correlated with HLA levels (? = -0.251, p = 0.14), and Breg levels showed a significant inverse correlation with DSA levels (? = -0.583, p = 0.002). The optimal cutoffs for predicting HLA and DSA positivity were =2.99 and =0.33 ×103/µL for Tregs and Bregs, respectively (p = 0.034, p <0.001). Conclusion This study revealed significant inverse associations between Treg levels and HLA antibodies, as well as between Breg levels and DSA, in kidney transplants. These findings underscore that enhancing Treg and Breg functions may offer therapeutic strategies to reduce HLA antibody or DSA-mediated complications. Further research is necessary to elucidate the mechanisms and to develop targeted therapies that modulate Treg and Breg activity for clinical benefit.