We focus on calcitriol’s actions in CD4+ T lymphocytes, but actions in other tissues, for example promotion of remyelination in the brain (130), insulin release from the pancreas (131), and intestinal barrier function in the colon (132), undoubtedly contribute to calcitriol’s potency as a chronic autoimmune and neurodegenerative disease inhibitor. Here, CD4 is linked to neurodegenerative disease.