Fig. 1.

Lymphocyte populations defined at the human enthesis. Thus far, two lymphocyte populations have been defined at the human enthesis. Innate lymphoid cells are part of the IL-23-responsive T cells which are residents of the healthy enthesis. Gamma delta T cells are also resident at the enthesis. The activation of resident T cells within the enthesis by IL-23 may promote inflammation, osteogenesis, and bone loss and remodeling. These lymphocyte populations may release different cytokines including IL-17 and IL-22 and TNF-α