These lymphocytes secrete cytokines. Cytokines are proteins that are assist in mediating the immune response to inflammation.[19] The presence of cytokines stimulates angiogenesis and MSCs differentiation into osteoblasts, which eventually constitute new bone. Chronic inflammation, which mimics aging, has been shown to negatively affect bone regeneration.[20] The exact reasoning behind the limit on inflammation needed for bone regeneration is not completely understood in the context of immune responses.