Cholesterol in the body is obtained from the diet or can be de novo synthetized. Cholesterol homeostasis is mainly regulated by the liver, where cholesterol is packed in lipoproteins for transport through a tightly regulated process.
Cholesterol in the cells helps the immune system fight off infections. LDL binds and deactivates bacterial toxins. For example, the MRSA (Methicillin-resistant Staphylococcus aureus bacterial) toxin does not destroy red blood cells when LDL is present.
HDL protect cells from infections by intracellular bacteria such as mycobacteria. Both mycobacteria and host-derived oxidized phospholipids inhibit innate immune responses; HDL from healthy subjects, which act as scavenger of oxidized phospholipids, can revert this effect.
Cholesterol levels also play important roles in immune cells such as monocyte priming, neutrophil activation, hematopoietic stem cell mobilization, and enhanced T cell production.
Considering that cholesterol is important in maintaining cell membrane stiffness, its importance to immune cells, one of the cell types relying the most on motility and membrane–membrane interactions with other cells, is easy to see.
In addition, changes in cholesterol intracellular metabolic enzymes or transporters in immune cells affect their signaling and phenotype differentiation, which can impact on atherosclerosis development.
Roles of cholesterol in immunity
