Research on infectious diseases, lung cancer, unstressed mice, the immune system, and Mycobacterium vaccae (M. vaccae) has led to the connection of the immune system with depression.
M. vaccae is a harmless bacterium found in the soil that may take the place of Prozac.
Oncologist Dr. Mary O'Brien tried out an experimental vaccine made from killed M. vaccae on lung cancer patients at the Royal Marsden Hospital in London. They improved in every way from fewer cancer symptoms, to better emotional and cognitive function.
Intrigued by Dr. O'Brien's results, Dr. Christopher Lowry of Bristol University put forth the hypothesis that perhaps M. vaccae would alleviate depression by causing the production of serotonin, the antidepressant messenger of nerve cells in the brain. Since the blood-brain barrier protects us from bacteria, how can this be?
The immune system has two kinds of activated Th cells: Th1 (T helper 1) and Th2 (T helper 2). Th1 cells attack pathogens within the cell, while Th2 cells attack pathogens outside the cells. Sometimes Th2 lymphocytes get out of hand, causing an exaggerated immune response or allergic reactions to harmless substances. They also interfere with the infection-fighting abilities of Th1.
Enter M. vaccae, which has a two-pronged effect. First, it stimulates T cells that immediately get to work restoring the balance between Th1 and Th2, diminishing allergic, tubercular, and cancer symptoms. Second, and this is where Dr. Christopher Lowry and his colleagues of Bristol University enter, it stimulates dendritic cells of organs such as the lungs and heart to secret cytokines. Dr. Lowry traced the action of the cytokines to the organs' sensory nerves, which sent messages to the raphe nucleus in the brain, which releases serotonin into the limbic or emotion center.
Dr. Lowry injected mice with M. vaccae. To find their stress levels, he put them in water. Stressed mice will not swim. The injected ones swam happily. Later their brains were examined to trace the path of serotonin.
There was a saying: "You have to eat a peck of dirt before you die." Did it mean that you had to eat dirt in order to have a healthy and happy life? Some people would say so.
This isn't the first study that implicates our super-hygienic lives, especially as toddlers, with difficulties later on. "These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn't all be spending more time playing in the dirt," according to Dr. Lowry.
References:
http://www.bristol.ac.uk/news/2007/5384.html
http://www.eurekalert.org/pub_releases/2007-04/uob-gdm033007.php
http://www.silence-therapeutics.com/index.php?option=com_content&task=view&id=31&Itemid=40
http://www.eurekalert.org/pub_releases/2007-04/uob-gdm033007.php
http://www.anapsid.org/cnd/diagnosis/cheneyis.html
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