FIGURE 4.

Possible mechanisms involving innate immunity in AS pathogenesis and responses to etanercept. Among monocytes, we identified MS2 (CD16⁺ monocytes, similar to nonclassical monocytes) as a peripheral blood mononuclear cell (PBMC) population present at lower proportion in AS patients. Treatment with etanercept recovered a higher proportion of MS2 in good responders. Among NK cells, a subtype similar to memory NK cells was induced and expanded in AS. In addition, CD16^medium/low NK cells were pathogenically activated in AS and did not respond to etanercept in any individual