ABSOLUTE NUMBER AND PERCENTAGE OF CIRCULATING NATURAL-KILLER, NON-MHC-RESTRICTED T-CYTOTOXIC, AND PHAGOCYTIC-CELLS IN UNIPOLAR DEPRESSION

One of the most consistently reported immunological abnormalities in m ajor depression is blunted ex vivo natural killer cell activity (NKCA) . This study was designed to investigate the number and percentage of circulating natural killer cells (NKC) in a group of patients with uni polar depression. In addition, the number and percentage of other phag ocytic/cytotoxic cells were determined. The following cell subsets wer e investigated: number of leukocytes, monocytes, neutrophils, lymphocy tes, NKC (CD16(+) or CD56(+)), and non-MHC-restricted cytotoxic T lymp hocytes (CTL) in 17 healthy controls and 79 depressed subjects. There were no differences either in absolute number or percentage of NKC, or CTL between healthy controls, minor, simple major, and melancholic de pressed subjects. Depression per se was characterized by a leukocytosi s due to monocytosis and neutrophilia. Our results do not support the thesis that depression-related blunted NKCA is caused by a decreased n umber or percentage of NKC in peripheral blood.