“…The cytotoxic potential of natural killer (NK) cell lymphocytes has been well studied recently (Herberman and Ortaldo, 1981), particularly in immunodeficient patients (Koren et aL, 1978), those with neoplasms (Hersey et al, 1979), and those who have other immune related medical illnesses (Kaufman, 1982;Merrill et aL, 1982). Since NK activity is proposed to be of major importance in the defense against the development and metastasis of neoplasms (Herberman and Ortaldo, 1981), as well as the protection against the occurrence of autoimmune illnesses such as rheumatoid arthritis (Goto et al, 1981), we hypothesized that schizophrenic patients may have higher NK activity relative to a normal population.…”