The underlying theory of blood type diets is that people with different blood types digest lectins differently, and that if people eat food that is not compatible with their blood type, they will experience many health problems.
Leptin is a potent stimulator of the immune system. Leptin receptors on monocytes cause the release intracellularly of STAT3 which cause the monocytes to release IL-6, IL-12 and TNF alpha. The IL-6 goes to the liver and increases production of CRP.
The production of red blood cells in the body is called erythropoiesis. Erythropoietin is a hormone that's made by the kidneys, and it tells the body to make more red blood cells. This hormone does pass into the breast milk, and it may help to stimulate the production of red blood cells in the newborn.