OBJECTIVE: Schizophrenia is a chronic psychotic disorder in which genetics and environmental factors such as infection and the corresponding immune response play a role in the etiopathogenesis. The aim of this study was to compare some immune factors such as nuclear factor-B (NF-B) activation, myeloperoxidase (MPO), the anti-inflammatory cytokine interleukin-4 (IL-4), and regulatory cytokine transforming growth factor- (TGF-) in schizophrenia patients and an age- and gender-matched control group.METHOD: Plasma levels of IL-4, TGF-, MPO, and NF-B activation in 20 subjects with treatment-resistant schizophrenia and 20 age- and gender-matched healthy controls were analyzed. Disease severity was evaluated using the Brief Psychiatric Rating Scale (BPRS).RESULTS: Plasma TGF- levels were found to be significantly lower and NF-B to be significantly higher in antipsychotic treatment-resistant schizophrenia patients than in controls in this study. No significant differences were found between the patient and control groups for serum IL-4 and MPO levels.CONCLUSION: The low TGF- level in treatment-resistant schizophrenia patients in the symptom exacerbation period indicates that there is inadequate Th1/Th2 balance. Large-scale studies are required to investigate whether this is responsible for resistance in schizophrenia. The fact that the increase in NF-B that we found in treatment-resistant schizophrenia patients in this study has also been reported in the first attack in untreated schizophrenia patients in previous studies indicates that NF-B plays a role in the disorder's physiopathology from the beginning.