Antidepressant drugs may have an effect on the immune system. Drugs such as Prozac and Zoloft, which belong to a class known as selective serotonin reuptake inhibitors, or "SSRIs," work by making the chemical serotonin remain for longer periods at nerve junctions.
New research indicates that serotonin is also a signaling molecule between immune cells. Dendritic cells pick up serotonin at inflammation sites and pass it along to T cells. This affects T cell growth and division into new cells.However, when Prozac was introduced at inflammation sites, it blocked this type of serotonin uptake.