C-Reactive Protein: The Most Familiar Stranger

C-reactive protein (CRP) is a highly conserved pentraxin with pattern recognition receptor–like activities. However, despite being used widely as a clinical marker of inflammation, the in vivo functions of CRP and its roles in health and disease remain largely unestablished. This is, to certain extent, due to the drastically different expression patterns of CRP in mice and rats, raising concerns about whether the functions of CRP are essential and conserved across species and how these model animals should be manipulated to examine the in vivo actions of human CRP. In this review, we discuss recent advances highlighting the essential and conserved functions of CRP across species, and propose that appropriately designed animal models can be used to understand the origin-, conformation-, and localization-dependent actions of human CRP in vivo. The improved model design will contribute to establishing the pathophysiological roles of CRP and facilitate the development of novel CRP-targeting strategies.