NATURAL-KILLER-CELL ACTIVITY IN MAJOR DEPRESSION - A PROSPECTIVE-STUDY OF THE IN-VIVO EFFECTS OF DESMETHYLIMIPRAMINE TREATMENT

To evaluate NK activity changes associated with both the diagnosis of major depressive disorder (MDD) and the in vivo treatment of MDD with the tricyclic antidepressant desmethylimipramine (DMI), 15 MDD outpati ents (11 females, four males) and eight controls (six females, two mal es) were evaluated prospectively at intake and after an average of 12 weeks of standardized DMI treatment. Plasma DMI concentrations at foll ow-up and severity of depression using the Extracted Hamilton Depressi on Rating Scale (EH) score at both intake and follow-up were also eval uated. At intake, NK activity was significantly higher in depressed pa tients compared to controls (P < 0.0001) while at follow-up NK activit y was not different between the two groups. NK activity decreased from intake to follow-up in depressed patients but not in controls. A seco nd analysis of NK activity was performed by dividing depressed patient s into responders and nonresponders (EH greater than or equal to 8 at follow-up). At intake, there was no difference between responders and nonresponders while at follow-up NK activity was lower in nonresponder s (P < 0.0001). Only nonresponders had a significant decrease in NK ac tivity from intake to follow-up. No correlation was found between DMI blood level and NK activity, and no difference in NK activity was pres ent between those with the highest and lowest DMI blood levels. Althou gh it is apparent that both MDD and its treatment influenced NK activi ty in this study, it is unclear whether the decrease in NK activity in nonresponding patients was a function of persistent depressed mood an d/or DMI treatment.