Delayed skin hypersensitivity reactions to human brain S-100 protein in psychiatric patients.

To confirm and extend previous observations concerning the correlation between cell-mediated immunity and psychiatric diseases, 511 patients with schizophrenia, cerebral atrophy, dementia, and mental retardation, and 32 control subjects and 27 control patients were skin-tested with human brain S-100 protein and human liver protein: 70.2-93.1% of tested psychiatric patients developed positive skin hypersensitivity reactions to S-100 protein, while 2.8-20.7% of patients reacted to liver protein. Of control subjects, 6.2-7.4% responded to S-100 protein, and 7.4-9.4% to liver protein. The findings indicate that cell-mediated immune processes may be involved in brain mechanisms underlying cerebral atrophy, depression, dementia, schizophrenia, and mental retardation.