We have not yet extended these studies to other cell types, such as Th1, NK, dendritic or other immune cells that could also be involved in AS.40 For example, reduced RUNX3 expression could enhance CD4+ T-cell activity, which would be consistent with models of AS invoking a pathological role for CD4+ T cells.41, 42 In particular, CD4+ Th17 cells have been implicated in AS and appear to be present in increased numbers in the peripheral blood of patients with pre-radiographical axial SpA43 and reactive arthritis.44 The gene discussed is CD4; the disease is reactive arthritis.