D3 dopamine receptor mRNA is elevated in T cells of schizophrenic patients whereas D4 dopamine receptor mRNA is reduced in CD4+ -T cells.

The expression of dopamine receptors was examined in purified human neutrophils, monocytes, B cells, natural killer cells and CD4+ - and CD8+ -T lymphocytes by RT-PCR. In healthy subjects, D1 and D2 receptors were not expressed in leukocytes. Real Time PCR for dopamine receptors D3 and D4 disclosed that D3 receptors are expressed in T cells and natural killer cells and D4 receptors in CD4+ -T cells. The comparison of schizophrenic patients with sex- and age-matched controls revealed a significantly higher expression of D3 receptor mRNA in T cells of schizophrenic patients, whereas D4 receptor mRNA in CD4+ -T cells was downregulated.