The production of two types of SAA protein—SAA1 and SAA2—is massively increased in the liver during the immediate immune response following an infection or during microbial colonization of the intestinal epithelium (Morrow et al., 1981; Ivanov et al., 2009; Reigstad et al., 2009; Derebe et al., 2014). The gene discussed is SAA1; the disease is infection.