Immunological abnormalities in schizophrenic patients have been reported for many years. However, the question of whether these parameters are involved in the pathophysiology of the disorder or represent treatment effects is still not answered. We investigated a combination of humoral and soluble immune parameters in 30 unmedicated schizophrenic patients before and during antipsychotic treatment and in 31 healthy controls. The aim of our study was to unravel an underlying immune process, to elucidate the influence of neuroleptic treatment and to identify a subgroup of schizophrenics. Antibodies against human 60-kDa heat-shock protein (HSP60), serum levels of soluble ICAM-1 and IL-2R were determined and correlated with parameters of blood-brain barrier and of psychopathology. In 10% of the drug-free but in 20% of the medicated schizophrenics, especially in females, we observed immunoreactivity against HSP60, high levels of IgG in CSF and a blood-brain barrier impairment. The high HSP antibody titres correlated with high levels of sIL-2R and sICAM-1. Only one of the controls showed antibodies against HSP60. Our results suggest that the observed immunological alterations are more pronounced during neuroleptic treatment than in the drug-free state. Whether or not this differential response to treatment with altered antibody production represents a subgroup of patients has yet to be determined.