TORONTO -- A study led by Boston University and in co-operation with the government of the central Pacific island nation of Kiribati has discovered new deep-sea microbes so foreign that human cells cannot recognize them or register that they exist.
The study, published March 12 in Science Immunology, challenges long-held beliefs in “universal immunity,” or that human cells can recognize any bacteria they interact with. The study’s findings say that some bacteria are solely defined by their local habitat or surroundings.
“Our team discovered and cultured novel microbes that are completely immunosilent to human immune systems,” co-lead study author and research assistant professor of biology at Boston University, Randi Rotjan, told a Boston University publication .
The study was the culmination of five years of research, with much of the lab work done at sea in a floating laboratory off the coast of Kiribati, the article said. The bacteria found and harvested in the study triggered no reaction or response from a human’s innate immune system.
“It’s generally assumed that [our innate immune system] can detect any microbe—or bacteria—we encounter, including from environments we are never exposed to, like the deep sea,” Rotjan said. “But the more our team spoke, the more it became clear that there are major gaps in our knowledge. No one had ever really tested the universality of the rules of immunity.”
Rotjan went on to describe that to deep-sea bacteria, “humans are Martians,” and vice versa.
“The novel bacteria from the deep sea that we collected and tested would never have had the natural opportunity to interact with humans—since they live thousands of metres below the surface,” Rotjan said.
“So, we asked the questions, what would happen when organisms from these distinct ecosystems interact? Fast-forward five years, thousands of plates poured, and an immeasurable number of conversations, we have evidence that the immune system of mammals has the ability to detect microbial bacteria from our home habitat, not habitats that are foreign like the deep ocean. The inability of immune receptors to detect most bacteria from a different ecosystem suggests that pattern recognition strategies may be defined locally, not globally,” Rotjan explained.
Rotjan said the implications of the study’s findings could lead to more discoveries on how host microbes interact in each ecosystem - opening up potential for “new biological tools and therapeutics,” like using the immunosilent bacteria as a way to deliver medicine or immune therapy.
