Part 3 in a series

If the immune system wants to learn which ingested proteins are good and which are troublemakers at birth, where would it go wrong?
The answer is very complicated, however, one of the driving factors seems to be the lack of exposure to friendly bacteria that act as an immune educator. This is the basis of the biome depletion theory. In the absence of this natural exposure and education, the immune system is believed to become intolerant to perturbations over time.
As we discussed last week, the military police/Treg cells are critical to the immune system’s ability to dampen inflammation after a robust response to an invading pathogen has occurred.
In order for the T regs to develop correctly, two major stimuli are necessary. First, we need adequate levels of vitamin D to turn on a gene called FoxP3, which in turn increases the production of the immune dampening beneficial Treg cells. Second, we need friendly bacteria in our intestines as they also have the ability to turn on FoxP3.
Achieving both of these goals comes from natural living where a child is exposed to adequate sunlight daily while being licked by a cat, dog or other animal that helps share good friendly bacteria.
In truth, the historical route of exposure was through human exposure to dust, dirt and food that had animal endotoxin in it from local animals.
Now this is only the beginning of the process for the immune system. As a child ages, these events must continue to keep the immune system primed and happy.
Assuming that your child has been delivered vaginally, was breastfed and had adequate microbial exposure in infancy while being exposed to the sun, does that mean that we are out of the woods?
The answer is no!
Let us look at the gut lining in a child. At the level of the intestine, children have a long row of cells that protect 70+percent of the immune system from being overtly exposed to the contents of the child’s diet and ingested pathogens. In proper tolerant function, the dendritic cells are situated between some of the gut cells, sending up a hand in between these cells to taste the intestinal world as bacteria and food slide by. This is really important! The system was set up to have a barrier wall between the outside world and us. This allows the immune system to keep bad guys in the intestine while memorizing them just in case they find their way to a sensitive location or grow in number, becoming pathogenic. Ingested food should be used by us as nourishment and not memorized as a bad guy, but as a helper.
What is keeping this area healthy? Why would it break down? Is this the point at which food allergies arise?
To answer these questions, we need to look closer at the gut cells.
These cells are simple long columnar cells that form a row, like soldiers in a line, that are held tightly together by tight junctions. They gather to make a really long tube we call the intestine.
As a child ingests food, it slides down into the stomach where it is digested into basic components. The beneficial nutrients travel onward and get absorbed in the small intestine, leaving the remaining material to pass all the way, until we have stool.
Soon after birth, the lining of the intestine is covered in bacteria, hopefully from breastfeeding and a vaginal delivery. These friendly bacteria produce all sorts of chemicals that support this healthy column of cells. They also help produce a mucous layer that lines the tube, adding another layer of protection. If everything goes well, then food proteins are utilized, bacteria and viral material are controlled, and life is good.

End of part 3

Dr. Chris Magryta is a physician at Salisbury Pediatric Associates. Contact him at newsletter@salisburypediatrics.com