IgA nephropathy (IgAN), the most prevalent primary glomerulonephritis, is a significant cause of chronic kidney disease. The heterogeneous clinical presentation and prognosis pose challenges in identifying patients at risk during the early stage of IgAN when kidney function is relatively preserved. This study aimed to characterize immune cell heterogeneity and transcriptional dynamics in IgAN patients stratified by disease severity. Peripheral blood samples were collected from 9 healthy controls and 17 biopsy-proven IgAN patients, who were classified into early- and late-stage disease groups based on estimated glomerular filtration rate at the time of blood collection. Single-cell RNA sequencing revealed distinct immune cell profiles and transcriptional changes between groups. Notably, early-stage IgAN featured a enrichment of IL-7Rahigh and IL-7Ramed effector memory (EM) CD8+ T cells, which showed distinct developmental trajectories relative to late-stage IgAN. These findings suggest a shift from memory CD8+ T cells in early-stage disease to IL-7Ralow EM CD8+ T cells in late-stage disease, correlating with disease progression (Figure 1). Trajectory and gene expression analyses revealed early-stage specific signatures, including pathways regulating T cell activation and differentiation (Figure 2). In contrast, CD4+ T cells and B cells exhibited limited correlation with disease progression. These results provide novel insights into immune cell dynamics in early-stage IgAN and underscore the prognostic significance of CD8+ T-cell subpopulations in IgAN progression. The findings highlight the potential of CD8+ T-cell subpopulation as therapeutic targets and offer a new strategy to delay IgAN progression.