Levels of monocyte reactive oxygen species are associated with reduced natural killer cell activity in major depressive disorder

Major depressive disorder (MDD) is associated with reductions in natural ki ller cell activity (NKCA), however the mechanism(s) mediating reduced NKCA in MDD has yet to be determined. In light of evidence that MDD is associate d with an inflammatory immune response, we propose that reactive oxygen spe cies (ROS), generated by inflammatory leukocytes (monocytes and/or neutroph ils), may mediate the suppression of NKCA in MDD, intracellular levels of m onocyte ROS were significantly associated with reductions in NKCA in outpat ients (n = 15) diagnosed with MDD. Sleep disturbance was also significantly correlated with reductions in NKCA. Elevated levels of ROS may be an addit ional characteristic of a subset of depressed patients in whom an inflammat ory response persists and elevations in ROS may, in part, mediate the assoc iations observed between MDD, cardiovascular disease, and cancer. Copyright (C) 2001 S. Karger AG, Basel.