In addition to Ahern, Peta Connell, Ph.D., from the Robarts Research Institute in Canada, was also a co-lead researcher on the study. Scientists from the Robarts Research Institute also contributed to the work.
In the brain, serotonin transmission between neurons is associated with feelings of pleasure, mood, and appetite, and the class of antidepressants known as SSRIs keeps serotonin active within the synaptic spaces between neurons, enhancing the chemical's positive effects. Unlike in the brain, which uses chemical messengers to communicate between nerve cells, the immune system is believed to "converse" through physical contact -- one type of immune cell touches another, setting off a response.
Specifically, "antigen presenting cells" display their antigens (bits of a foreign invader) to T-cells, and a resulting physical coupling between the antigens and the T-cells will prompt the T-cells to divide and expand in population, triggering an immune response designed to destroy the invader. This process may take hours.
What the Georgetown researchers found, however, is that dendritic cells -- the most powerful of the antigen-presenting cells and the ones that can find invaders that have never infected the body and "educate" the immune system to fight them -- also use serotonin to quickly excite a T-cell response. They discovered that these dendritic cells can rapidly secrete serotonin, which activates serotonin receptors on certain types of T-cells.
"In addition to the physical contact, it surprised us to find that these immune cells also have machinery to take up serotonin and to secrete it in an excitatory manner," Ahern said. "The point behind this transmission is not entirely clear, but it appears to be an additional way of stimulating a T cell response."
Drugs that block serotonin reuptake "likely change some of the parameters of T-ce
Source:Georgetown University Medical Center