CD163 and interstitial nephritis: Although in vitro studies indicate that M1-polarized macrophages express higher levels of 1α-hydroxylase than M2 macrophages (20), the in vivo microenvironment of IgG4-related tubulointerstitial nephritis is dominated by CD163+ M2-like macrophages, within which 1α-hydroxylase was observed to co-localize.