In the current study, we investigated the microRNA expression profiles of negatively regulating TLR4 signaling, including the measurement of let-7e, miR-21-5p, miR-223, miR-145, miR-146a, and miR-155 in the serum exosome obtained from patients with MDD before and after treatment with antidepressants. The gene discussed is TLR4; the disease is major depressive disorder.