#2899 Role of the Th17.1 cells in IgA nephropathy

Abstract

Abstract Background and Aims T helper (Th) cells play a crucial role in glomerulonephritis, including IgA nephropathy (IgAN). Recently identified Th17.1 cells, which are elevated in sarcoidosis, lupus, and Takayasu arteritis, express chemokine receptors CCR6 and CXCR3. These receptors are implicated in inflammatory cell infiltration and fibrosis in glomerulonephritis models. Notably, Th17.1 cells express MDR-1 (multidrug resistance protein) and the drug efflux protein p-glycoprotein, associated with corticosteroid resistance. However, the exact role of Th17.1 cells in IgAN remains unclear. Intriguingly, Th17.1 cells produce INF-γ and IL-17, cytokines implicated in IgAN pathogenesis. Method In this retrospective cross-sectional study, we examined circulating Th17.1 cells in 18 confirmed IgAN patients. Antibodies such as anti-CXCR3-FITC and anti-CCR6-PCy7 (Biolegend, U.S.A.) were used to stain Th subpopulations. We also used combinations of the following antibodies: anti-CD45-FITC, anti-CD4-PE, anti-CD8-ECD, anti-CD3-PCy5, anti-CD56-PCy5, anti-CD3-PCy7, anti-CD19-ECD, anti-CD127-FITC, anti-CD25-PCy5, and anti-CD4-PCy7 (Coulter Immunotech, France) to evaluate T, B, NK, and Treg cells. Multicolor flow cytometry was performed using a Navios cytometer, and data were analyzed using Kaluza software (Beckman Coulter, U.S.A.). Th effector subpopulations of CD4+ lymphocytes were identified based on chemokine receptor expression: Th17.1 (CXCR3+CCR6+). Th17.1 cells were quantified as a percentage of CD4+ lymphocytes. Th1, Th2, and Treg cells were also evaluated. We explored correlations between Th17.1 cell counts, estimated glomerular filtration rate (eGFR, mL/min/1.73 m²), and proteinuria (24-hour collection). Among the patients, 5 were classified as refractory (progressive eGFR decline > 5 mL/min/1.73 m² and 24-hour proteinuria > 1g despite steroid and immunosuppressant therapy). Results The study included 18 patients. The mean (95% CI) Th17.1 cell count was 20% (16-23), and the 24-hour proteinuria was 2.1g (1.4-2.7). A significant direct correlation was observed between Th17.1 cells and proteinuria (g/L, adjusted for 24 hours) (r = 0.50, P = 0.03). Refractory patients exhibited higher Th17.1 levels compared to others (25% [95% CI: 17-33] vs. 18% [95% CI: 14-21], P = 0.02) (Fig. 1). Patients with proteinuria < 0.5g/24 h had lower Th17.1 cell counts compared to those with higher proteinuria (16% [95% CI: 12-20] vs. 21% [95% CI: 17-25], P = 0.06. No correlation was found between eGFR, proteinuria, and Th1, Th2, Th17, or Treg cells. Conclusion These findings suggest that Th17.1 cells may contribute to the pathogenesis of IgAN and could potentially indicate the response to steroids or immunosuppressants in treatment. While the direct involvement of Th17.1 cells in kidney tissue remains unexplored, further investigation is warranted due to its therapeutic and prognostic implications.