CD4 and systemic lupus erythematosus: The analysis of immune cell heterogeneity within and among patients with SLE revealed several key findings: (1) the identification of >20 distinct cell subsets actively involved in disease pathogenesis, (2) global and cell type-specific expression of interferon gene signatures across various immune cells and (3) differences in certain cellular compositions in comparison to controls, such as a decrease in naive CD4 T cells and an increase in repertoire-restricted CD8 T cells.