Emerging evidence for the role of neurotransmitters in the modulation of T cell responses to cognate ligands

Dendritic cells (DCs) are responsible of priming T cells and promoting their differentiation from naïve T cells into appropriate effector cells. Each different phenotype of effector T cells promotes the elimination of a determined kind of pathogen or tumour. Thus, DCs and T cells play critical roles on orchestrating adaptive immune responses against specific threats. Because of their fundamental functions at controlling immunity, DCs and T cells require tight regulatory mechanisms to ensure efficient, but safe, immune responses. Several studies have shown that neurotransmitters, in addition to mediate interactions into the nervous system, can contribute to the modulation of immunity by promoting the communication between nervous and immune systems and in the interaction between different immune cells. Due to the pivotal role that the DC-T cell interaction plays in the development and regulation of adaptive immune responses, it is important to understand how the function of these cells may be regulated by neurotransmitters. Here, we review the emerging role of neurotransmitters as regulators of DC and T cell physiology and also how these molecules, by acting on the DC-T cell interaction, may modulate the fate of T cells and, therefore, the nature of the adaptive immune response. Moreover, we discuss how alterations on the neurotransmitter-mediated immune regulatory mechanisms can contribute to the onset of immune-related disorders. In addition, we discuss potential new targets for the design of strategies for therapies against tumours, autoimmunity and neuro-immune related diseases.