NK cells in lymph nodes are ordered by a kind of protein flowing in lymph and go to patrol all over the body. It is considered that NK cells are stimulated by the flow of this protein and go to patrol. But if the flow of lymph is not good, the amount of the protein flown in lymph nodes decreases and NK cells tend not to go to patrol, leading to the lowering of the immune strength.
So if you can make the flow of lymph better, NK activity goes up and the easiest method to make the flow of lymph better is lying down.
Lymph tends to stagnate because lymph doesn’t have a pump like heart for blood, so if you stand or sit for a long time, lymph tends to accumulate in lower body by the influence of the gravity. Lying down makes the flow of lymph better and the lymph stagnated in the lower body goes back to the upper body, a large amount of the protein flows into lymph nodes, NK cells taking a rest are stimulated and start going to patrol.
While you are lying down, performing abdominal breathing is more effective. There is cisterna chyli in the abdomen (Fig. 3), where lymph coming from the legs and the intestines is stored, like a tank. Cisterna chyli enlarges when lymph flows in. If you perform abdominal breathing to raise up the abdominal pressure, the stored lymph flows out in one go. At that time, it is important that the lymph from the intestines flows well because the intestines are connected to the outside and invaded by foreign substances so there are a lot of the best immune cells. If you can flow the lymph stored in cisterna chyli, you can send the best immune cells all over the body through lymph.
Why do you have to lie down after a meal?