IPP and brain disorder: In healthy individuals, the percent of γδ T cells within the total CD3+ T cell population is generally stable over time, and only change in specific stimulatory circumstances, for example, when patients are treated with intravenous administration of bisphosphonate for osteoporosis, which increases monocyte expression of IPP, a γδ T cell antigen, or in multiple sclerosis patients with active brain disease, by unknown mechanisms [20,21].