T- Cells can produce Neurotransmitters: A bridge between Adaptive Immunity and Brain Function?

Apart from the conventional role of T cell in immunity, their presence in the nervous system has provided a glimpse to interaction between immunology and neurology. Adaptive immunity has been less studied which plays a significant role in brain function. T cells appear to be significant in a) learning and memory and b) Decrease of pro-inflammatory response not only through cytokines production but also by regulation of neurotransmitter release. It has been reported that stimulation of vagus nerve activates the spleenic nerve which activates CD4+ T cells to release acetylcholine. That certain populations of memory T cells have capacity to produce acetylcholine is certainly an interesting finding which could pave way for reciprocal interaction between the neural and immune system. In 2011, it was proved that T cells not only possess Choline Acetyl Transferase (ChaT) but also express α7 nAchR which interact with TCR. Interaction of α7 nAchR with TCR activates TCR/CD 3 complex reported to be involved in the process of Long Term Potentiation (LTP) critical for memory formation. Moreover, T cell–derived IL-4 has been shown to play a dual role in the maintenance of cognitive function and also antagonize the deleterious effects of pro inflammatory cytokines on astrocytes and neurons in brain. Various studies have demonstrated that T cells could decrease inflammation through separately through their dopamine D1, D5 receptors via D1R/D5R-cAMP-PKA-CREB signaling pathway and as well as via acetylcholine α7 nAchR leading to finally suppress of IL-12 and IL 10 production. Presence of T cells though noted in CSF has been noticed but how they migrate in and out of CSF is not clear. Here we would like to elaborate upon possible interaction between neurotransmitters and T cell interaction to mediate critical functions of learning, memory formation and modulation of pro-inflammatory response.