Higher natural killer cell activity in schizophrenic patients: The impact of serum factors, medication, and smoking

Schizophrenia has been associated with altered immunity and reduced occurre nce of autoimmune diseases and malignancies. A few studies in schizophrenic patients have assessed natural killer cell activity (NKA), but no consiste nt findings have emerged. However, NKA was assessed using standard procedur es and in the absence of autologous serum and the various cytokines that mo dulate NKA and appear to be abnormal in schizophrenic patients. In the curr ent study, therefore, the number of NK cells and the activity of the indivi dual NK cell were assessed in whole blood shortly after blood withdrawal, i n both the presence and the absence of autologous serum. Twenty-nine schizo phrenic patients (11 nonmedicated), 8 nonschizophrenic control patients (bi polar and personality disorders), and 31 age-matched healthy controls were studied. Schizophrenic patients showed higher NKA per NK cell than controls and nonschizophrenic patients. This difference remained significant even w hen the nonmedicated schizophrenics, who showed the highest levels of NKA, were excluded. However, the increase in NKA was more pronounced in the pres ence of serum and was reduced to an insignificant level when serum was remo ved from the same samples. In both schizophrenic patients and controls, smo kers and women showed lower NKA. Numbers of NK cells did not differ among g roups, although medication affected blood concentration of other leukocytes . These findings indicate that the effects of serum factors, psychiatric me dication, gender, and smoking should be considered when assessing NKA in sc hizophrenic patients. The observed higher NKA may help explain the surprisi ng reports of low incidence of lung cancer and other malignancies in schizo phrenic patients, despite their higher rate of smoking. (C) 2000 Academic P ress.