Abstract: An association between inflammatory abnormalities and schizophrenia has been found repeatedly. In the current study, schizophrenia was induced by MK-801 (0.35 mg kg-1, i.p.) twice a day for 2 weeks in rat pups. We found serum levels of IL-2, IL-6 and immunoglobulins were significantly higher than the normal level but TNF-α levels were significantly suppressed after the treatment of MK-801 in neonatal rats. Clozapine or haloperidol treatment could reverse immunoglobulins and TNF-α levels. However, clozapine, not haloperidol, did not recover serum levels of IL-2 and IL-6. T-cell subsets in peripheral blood of model rats were significantly increased in adulthood. On the contrary, the rate of CD4 (+)/CD8a (+) T cells was reduced significantly. After the treatment of clozapine or haloperidol, the levels of T-cell subsets were restored. However, clozapine, not haloperidol, has no effect on the rate of CD4 (+)/CD8a (+) T cells. These results suggested that the dysfunction of cytokine system and immune disturbance may be involved in the pathogenesis of MK-801-induced rat model of schizophrenia. The effects of clozapine and haloperidol on cytokines production, T-cell subsets switch and immunoglobulins presented in this study indicated that immunomodulatory therapy may be a potential strategy in the treatment of schizophrenia.