Correlations between major depressive disorder, splenic morphology, and immune function.

To analyze the symptoms, courses, and severities of depressive disorder, as well as the morphological changes in the spleens and related immune mechanisms, we recruited patients with first-episode or recurrent major depressive disorder (MDD) (patient group) and healthy controls (normal group) matched in age and gender. We measured their plasma MICB (pg/ml), ULBP1 (ng/ml), and splenic volume (cm3) at baseline. The patient group was randomly assigned to receive (S)-ketamine (study group) or saline (control group), and the above indices were collected again on the 4th weekend after administration. At baseline, both MICB and splenic volume were significantly higher in the patient group than in the normal group. A positive correlation was observed between MICB and splenic volume in the patient group. After (S)-ketamine administration, the elevated splenic volume and MICB levels decreased. These results suggest that the pathogenesis of MDD may involve abnormal MICB expression and splenic morphology. (S)-ketamine may ameliorate inflammation and enhance splenic function, thereby relieving MDD symptoms.