CD4 and systemic lupus erythematosus: The percentages of CD3+, CD3+/CD4+, CD3+/CD8+, CD4+/CD8+, CD3−/CD16+ CD56+, and CD3−CD19+ in the peripheral blood of patients (n = 80) classified into lupus nephritis, blood involvement, and joint involvement and SLE in different active stages were detected by flow cytometry.