HSPD1 and infection: In addition, increasingly more studies have shown that some other pathogen-associated molecular patterns (PAMPs) can promote immune responses through the TLR4, such as heat shock protein 60 (Hsp60) (58, 59), and Hsp60 exists in M. hyopneumoniae; another study shows that Hsp60 has good immunogenicity in the first natural infection of M. hyopneumoniae (60), which suggests that the capsule or Hsp60 of M. hyopneumoniae may play an important role in promoting the secretion of IgA.