Cross-Talk: Immunity and the Psyche

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Discovered in the early 1980’s as immune system components, nobody predicted that cytokines would be recognized as “communication molecules” that linked the immune system to the psyche. “Cross-talk” is the jargon for this type of interaction as the same molecules are used to regulate totally different systems.

The breakthrough experiment for this discovery came with cancer patients suffering from hepatitis. Injected with cytokines in the hopes of boosting their immune protection, these patients instead developed acute psychosis or depression. In the experimental “infection protocols,” increased cytokine production led not only to fever and elevated stress hormones, but also to a decrease in the neurotransmitter serotonin.

This may be the way to connect meditation and cytokines, for meditation has been tied to serotonin for some time. Several studies show that there is a significant increase in the urinary excretion of the serotonin metabolite, 5-HIAA, in people practicing TM. This increase in serotonin metabolism may indicate an increase in the functioning of serotonin in the brain. The author of a 1976 study dubbed serotonin “the rest and fulfillment hormone.” Serotonin is a potent modulator of limbic/amygdala activity- the brain center controlling our emotions. In 2003, an article in the American Journal of Psychiatry concluded that the serotonin system may serve as the biological basis of spiritual experiences. Curiously, humans appear to have a wide genetic variance in this system, which may explain why people vary so much in their “spiritual zeal.”

The subtleties of serotonin physiology are so complex that in the end, even after the millions of dollars spent in research by the pharmaceutical industry on serotonin-we don’t even know how Prozac exactly works. By comparison, meditation is a vast, unexplored territory. However, I think it is safe to conclude this much: Cytokines affect serotonin metabolism. Meditation affects serotonin metabolism. Since biology always strives for balance, I will bet anything that as serotonin metabolism is changed through meditation it pushes back upon the cytokines

Maharishi, in his mystic wisdom, often described stress as “tying knots in the nervous system.” What does this mean beyond the simple metaphor of stress giving you a knot in th stomach? Curiously, neuronal plasticity (an obvious candidate for the tying and untying of the knots) now appears mediated in part by IL-1, IL-6 and TNK-a. In fact, in another great surprise and example of cross-talk, other immune molecules, those from the major histocompatibility complex (MHC), have also been found to “remodel the nervous system.” At first blush this is the strangest of results a biologist might come across. MHC molecules shaping neural circuits! These molecules gained fame by establishing tissue type and causing problems in organ transplants. They are why transplant patients have to have their immune systems knocked out before the transplant can be accepted.

Why would these molecules be used to change neural circuitry? No one ever expected them to be used in brain development, but in the definition of immunity lies a metaphor of beauty. By definition the immune system is that which defends us from infection. The immune system can only do this by discriminating between what is self and non-self. Biologically, this means recognizing what tissue is mine and what tissue is other, which cell in mine and which cell bacterial. That’s what immunity is all about.

And how might one define meditation? It too is the process of discriminating self from non-self. In an unenlightened state we mistake our true Self for all those external things: the roles we play, the status we obtain. We are totally identified with our senses and desires. The first steps to enlightened vision must separate Self from all this non-self and little self. And so each tradition introduces a favored means of purification.


The immune system at one level roots out non-self by rejecting foreign tissue or bacteria. This purification creates wars of allergies and fever. On another level it may root out non-self by altering our nervous system. In his commentary on the Bhagvad Gita, Maharishi spoke of the “battle field of life.” Here, the struggle is fought within our own consciousness as we master discrimination of the Self. Perhaps it’s only parsimonious that the body uses the same molecules at both levels of endeavor.