For example, schizophrenia has been associated with increased numbers of DRD4 cell surface-expressing CD4+ and CD8+ T cells [44]; and increased lymphocyte gene expression of DRD3 [45, 47] (but not DRD4) has been reported in three independent prior studies, including in patients not treated with anti-psychotic drugs [47]. This evidence concerns the gene DRD3 and schizophrenia.