Circulating Mitochondrial DNA Alerts Immune System to Danger

In response to short DNA fragments, lymphocytes release mitochondrial DNA that helps trigger an immune response.

Katarina Zimmer
Mar 1, 2018

SPIDEY SENSE: Lymphocytes ejected weblike, fluorescing strands of mitochondrial DNA (green) when exposed to certain oligonucleotides. PNAS

EDITOR'S CHOICE IN IMMUNOLOGY

THE PAPER
B. Ingelsson et al., “Lymphocytes eject interferogenic mitochondrial DNA webs in response to CpG and non-CpG oligodeoxynucleotides of class C,” PNAS, 115:E478-87, 2018.

MOLECULAR BATTLEGROUND
Beyond acting as a genetic blueprint, DNA can play a direct role in the immune system. For instance, neutrophils cast webs of DNA and antibacterial proteins into the bloodstream to trap pathogens. When a team of Swedish researchers observed that B lymphocytes also appear to eject DNA, they decided to investigate further.

IMMUNE ARTILLERY
The researchers isolated several types of lymphocytes—B cells, T cells, and natural killer cells—from healthy blood donors and leukemia patients. They exposed them to a variety of triggering molecules, such as ionomycin from Streptomyces conglobatus, together with a fluorescent DNA-binding substance in vitro. Only when exposed...