ACTA1 and temporal arteritis: Greigert et al. described a positive feedback loop by which myofibroblasts (CD90+α-SMA+MYH11+) located in the neointima of GCA-affected temporal arteries produce Th1/Th17 polarizing cytokines (IL-12/IL-23) in response to IFN-γ and TNF-α, thereby sustaining T cell polarization [27].