Immune-histochemical (IHC) analyses of LPS, TLR4 and CD68 in carotid plaques and superior thyroid arteries. Immunostaining for LPS and TLR4 and cell phenotype in carotid atherosclerotic plaque (A) and thyroid artery (B). Serial sections (2 μm) were prepared as described in Online Methods and stained with hematoxylin and eosin. The presence of the antigen recognized by the primary antibody is indicated by a brown substrate. IHC analysis revealed immunoreactivity for antibodies against LPS from Escherichia Coli (EC) (A1, 10X), TLR4 (A2, 10X) and CD68 (A3, 10X) in three serial sections of carotid plaque particularly in the area associated with necrotic lipid core (asterisk). Immunostaining for anti-LPS, anti-TLR4 and anti-CD68 reveals no reactivity in thyroid arteries (B1–B3, 10X). Negative control, with a rabbit preimmune serum, in the area of the plaque near the lipid necrotic core and thyroid artery section (A4 and B4, 10X). A view of Panels A1–A3 and Panels B1–B3 at higher magnification was reported (40X).