CD4 and major depressive disorder: In addition, there were nine factors of lymphocyte subsets that were significantly different between the MDD and BD groups, included CD19+ B cell counts, CD3+ T cell counts, CD3+/CD4+ T-helper cell counts, CD3+/CD4+ T-helper cell (%), CD3+/CD8+ T cell counts, CD3+/CD8+ T cell (%), CD3–CD16/56+ NK cell counts, CD4+CD8+ (ratio), and total lymphocyte counts.