Immunophenotypic Characterization of LAMP-1 on Cytotoxic T Cells in Systemic Lupus Erythematosus Patients and Its Correlation with Disease Activity

Background: Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease in which cytotoxic T cells contribute to tissue damage through dysregulated effector pathways. CD107a (LAMP-1) serves as a functional marker of CD8+ T-cell degranulation and may reflect disease-related alterations in cytotoxicity. Objective: To investigate the expression of CD107a on cytotoxic T cells in SLE patients and evaluate its relationship with disease activity and immunological features. Methods: Demographic, hematological, and immunological profiles of SLE patients and controls were compared. Flow cytometry was used to evaluate CD3+, CD3+CD8+, CD4+, double-negative T cells, and CD107a+CD8+ subsets. Correlations with disease activity and diagnostic performance were assessed. Results: SLE patients showed anemia, thrombocytopenia, and lymphopenia compared with controls. Immunophenotyping revealed significantly elevated CD3+CD8+, CD107a+CD8+ T cells in SLE, and reduced CD4+ counts. While CD107a+CD8+ levels were strongly elevated, they did not correlate with disease activity scores, suggesting persistent upregulation of CD107a expression independent of clinical severity. ROC curve analysis indicated that CD3+ and CD3+CD8+ subsets had diagnostic utility, while double-negative T cells showed additional value. Conclusion: SLE is associated with increased CD107a+CD8+ T cells, reflecting heightened basal expression of this degranulation marker regardless of disease activity level. These findings underscore the role of altered cytotoxic T-cell function in SLE immunopathogenesis and support CD107a as a potential biomarker of immune dysregulation.