TLR9 and cryptosporidiosis: Furthermore, undernourished APOE4 targeted replacement (TR) mice infected with Cryptosporidium parvum, a protozoon commonly associated with diarrhea in children living in endemic areas of malnutrition, showed a more regulated inflammatory response and more efficient pathogen elimination with higher levels of Toll-Like receptor 9 (TLR9) transcripts which are mediators of the innate immune system against Cryptosporidiosis (Azevedo et al., 2014).