Stories about: bacteria

Another microbiome perspective: The host holds the leash

Abstract depiction of the microbiome

Most scientists and clinicians accept that the human microbiome impacts a person’s nutrition, immune system function, physical health and perhaps even mental illness, but exactly how or why is not well understood. Now, taking an evolutionary approach, a Boston Children’s Hospital infectious disease researcher suggests the host may play a more active role in controlling the microbiome than previously appreciated.

“I think we need to re-evaluate the way in which we think about the microbiome,” says Seth Rakoff-Nahoum, MD, PhD, a physician-scientist at Boston Children’s in the Divisions of Infectious Diseases and Gastroenterology, whose perspective was published today in Nature.

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Our T-cells have been hiding something: Another way to kill bacteria

Listeria intracellular bacteria infection T-cell immunity granzymes granulysins
Listeria bacteria on a plate. The biology of HIV/AIDS suggests T-cells have a hitherto unrecognized way of killing pathogens like these.

The immune system, despite its immense complexity, really has only a few ways to kill bacteria:

  • Neutrophils and macrophages can capture and digest extracellular bacteria (ones that live free in tissues and the bloodstream).
  • Peptides (protein fragments) can punch holes in bacterial membranes or cross the membranes to disrupt bacterial processes.
  • T-cells can kill cells infected by intracellular bacteria (ones that take up residence within cells).

It’s this last mechanism that I want you to pay attention to. The conventional wisdom has long held that T-cells can only kill intracellular bacteria indirectly by eliminating the cells they’ve infected. But a paper by Judy Lieberman, MD, PhD, of Boston Children’s Hospital’s Program in Cellular and Molecular Medicine, reveals that T-cells have a hitherto unnoticed way of directly killing intracellular bacteria And she only found it because of HIV/AIDS.

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