C. elegans uses small RNAs to defend against viruses by destroying them.

“These worms don't have dedicated immune cells like we do. They don't have T cells or B cells. They defend themselves from viruses very efficiently using RNA. So, in fact, when we started these experiments, there wasn't any natural virus that was known to infect clients, which is amazing because viruses are very good, as we all experience now, in infecting. And the worms are resistant to viruses because of RNA molecules, short RNA molecules that destroy viruses. And these are called small RNAs.”