Dopamine sends immune signals too

Nerve cells often communicate chemically. One cell releases packets of molecules called neurotransmitters, which then influence the behavior of another neuron. Dopamine is one such neurotransmitter known to carry signals in brain circuits involved in rewarding behavior and motor control.

Now scientists report that dopamine also ferries messages between immune cells outside the brain to promote antibody production (Nature 2017, DOI: 10.1038/nature23013).

When a pathogen invades the body, immune cells that recognize the threat become active and migrate to lymph nodes or the spleen. Once there, activated T cells and B cells “talk” to each other through immunological synapses—similar to the structures used in nerve cell communication. The conversation between the cells further activates them, including triggering the B cells to mature and start producing antibodies to clear the infection.

Ilenia Papa and Carola G. Vinuesa of the Australian National University and coworkers studied immune cells from human tonsils, spleens, and lymph nodes and determined that the T cells in the samples contained granules filled with dopamine. These granules are similar to those carrying dopamine and related neurotransmitters in nerve cells.

In cell culture experiments, the team found that human B cells exposed to dopamine move proteins important in immune responses to their surfaces. This triggers a feedback loop that helps strengthen the synapses between T cells and B cells and pushes the B cells to mature.

The findings, Papa says, could lead to strategies to enhance dopamine signaling to boost vaccination responses or to disrupt it to block the production of autoantibodies in autoimmune diseases.