C3 and myeloid sarcoma: The relative extent of C1q immunoreactivity was increased at perivascular sites in cortical and subcortical areas of MS brain (Figure 2B), whilst the extent of C4d, Bb, and C3b immunoreactivity was increased in comparison to control and inflammatory disease controls at leptomeningeal/pial sites, and at perivascular/parenchymal sites in the GM and WM (Figures 2C–E).