Figure 2.

The Iron Curtain. Iron-laden macrophages occupy a unique cellular niche in the tumor where they act as an interfacial boundary mediating systemic and microenvironment metabolic flux and immune response. Prussian Blue iron histochemistry which is specific for ferric iron deposits from endogenous hemosiderin (shown here) or iron nanoparticle contrast agent (not shown) in such macrophages beside pan-macrophage CD68 immunohistochemical staining reveals a distinct spatial pathology of such iron-laden macrophages suggestive of an “Iron Curtain” where colonies of TAMs exhibiting similar iron accumulation phenotypes form physical borders in the TME.