UC Irvine microbiologist Manuela Raffatellu has found that our immune response can sometimes make us vulnerable to the very bacteria it’s supposed to protect us from. A study published today in the journal Immunity reveals that the immune protein interleukin-22 enhances the growth of dangerous bacteria–such as salmonella, which causes food poisoning–and curbs the proliferation of healthy bacteria commonly found in the gut. “Surprisingly, we found that interleukin-22 not only fell short in protecting the host against the spread of salmonella but was actually beneficial to these harmful bacteria,” said Raffatellu, an assistant professor of microbiology & molecular genetics. “Our findings have important implications for the development of treatment strategies against pathogens that can resist interleukin-22-induced responses.” While IL-22 does not protect against all pathogens, the protein still plays a crucial role in controlling the spread of some harmful microbes. “Blocking interleukin-22 during infection would be too detrimental to the host, so a more promising therapeutic strategy would be to specifically target the alternative pathways used by salmonella and, potentially, other pathogens to evade interleukin-22’s defenses,” Raffatellu said.