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.
Leptin is produced primarily in the adipocytes of white adipose tissue. It also is produced by brown adipose tissue, placenta (syncytiotrophoblasts), ovaries, skeletal muscle, stomach (the lower part of the fundic glands), mammary epithelial cells, bone marrow, gastric chief cells and P/D1 cells.