The nerve systems affect immune functions by releasing neurotransmitters through lymphocyte cell-surface receptors. A major neurotransmitter dopamine transmits signals via five different seven-transmembrane G protein-coupled receptors termed D1 to D5. There is wide evidence for a decreased risk of rheumatoid arthritis (RA) in patients with schizophrenia which is associated with the excessive stimulation of D2-like receptors by dopamine. However, the reason for the negative association between RA and schizophrenia is unknown. We previously demonstrated that dendritic cells (DCs) could synthesize and store dopamine, DC released dopamine to naive CD4 T cells upon DC-T cell interaction and affected helper T-cell differentiation. Because DCs have been proposed to play a pivotal role in the initiation and perpetuation of RA by presentation of arthritogenic antigens to T cells, we here assessed effects and functions of dopamine on immune cells during the pathogenesis of RA. In this paper, we overview the series of our research findings, and present the possibility of drug discovery which target at dopamine receptors.