January 24, 2007 | David F. Coppedge

Your Body Knows Its Allies at Gut Level

How come your body doesn’t fight its good bacteria?  It sounds like a question only a scientist or a kid would ask, but think about it.  Your body jumps to arms to fight off pathogens, but lets millions of bacteria live in the intestines.  These bacteria help you digest your food, but are not “you.”  What is it that keeps these invaders from alerting the cops?  Do they carry a green card or something?  Sort of; their employers do.
    Margaret McFall-Ngai discussed this concept in a Nature essay Jan. 111 (see also EurekAlert Jan. 9).  It was known that the pancreas has dendritic cells that put the immune system at ease by placing antigens of friendly allies on cell surfaces.  A similar but different signalling mechanism is at work in the intestine.  Stromal cells from lymph nodes train the immune system’s police, the T cells, to tolerate the intruders as good guys.  The EurekAlert article ends with this quote from Shannon Turley, co-author of a study in Nature Immunology:

“Our study points to a previously unknown mechanism of immune system tolerance,” Turley explains.  “When you think of the conditions in the small intestine, with so many millions of bacteria cells and so much opportunity for dendritic cells to stimulate an immune attack, it’s remarkable that intestinal tissue is so rarely the target of an immune attack.  Our findings demonstrate that the immune system has features that remain to be discovered.


1Margaret McFall-Ngai, “Adaptive Immunity: Care for the community,” Nature 445, 153 (11 January 2007) | doi:10.1038/445153a.

When you say grace for a meal, you can now mean it from the gut.  In the ancient near east, the bowels were considered the seat of the emotions.  Talk to your stromal cells, T cells and bacterial allies like Paul did to Philemon, “Yea, brother, let me have joy of thee in the Lord: refresh my bowels in the Lord.”  (Works best when you send down regular donations of healthy provisions.)

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