The authors found that LPS, but not low pH, increased the expression of proinflammatory cytokines, indicating the capacity of cells from the stratum spinosum and basale to respond to LPS, presumably via TLR4. Furthermore, mRNA of several APP (haptoglobin,SAA, LPS binding protein, α-1 acid glycoprotein) was detected in ruminal tissue of healthy cattle, although by immunohistochemistry, only haptoglobin and α-1 acid glycoprotein were localized in the superficial layers of ruminal epithelium (Rahman et al., 2010; Dilda et al., 2012).