Figure 9.
Immunohistochemical analysis of TLR4 in rat, murine, and human cardiac muscle. Photomicrographs are shown for primary isolates of ventricular myocytes isolated from adult rat hearts (×400) 24 hours after isolation, stained with a polyclonal Toll antibody targeted to a TLR4-specific epitope adjacent to the cytoplasmic TIR domain of hTLR4. Absorption with the peptide used to generate the primary antibody (Anti-Toll + peptide) and substitution of the primary antibody with a control rabbit antiserum (Control serum) were used as controls. Both normal murine cardiac muscle (×200), as shown here, and sham-operated murine cardiac muscle and normal rat cardiac muscle (not shown) exhibited diffuse, homogeneous myocyte staining. However, cardiac myocytes adjacent to an area of ischemic injury (Infarct) in the mouse exhibited intense sarcolemmal staining for TLR4. Note the absence of significant staining of infiltrating inflammatory cells (×400). Finally, in samples from both humans with a dilated cardiomyopathy (bottom left panel) and in remodeling murine ventricular muscle remote from the site of ischemic injury (not shown), intensely stained focal expression of TLR4 was observed in adjacent regions of 2 or more juxtaposed cardiac myocytes (×600). This intense focal staining pattern for TLR4 was not observed in sections of normal human myocardium (not shown).