Mitochondria produce their own immune weapon
Mitochondria do more than generate energy. They also produce a peptide that directly attacks bacteria and reprograms immune cells. That makes them an unexpected part of your body’s defenses.
For a long time, the immune system was assumed to be encoded entirely by the nuclear genome. Mitochondria, the cell’s power plants, were not thought to play an active role. That picture has now changed. The study, published in eLife, shows that the mitochondrial genome encodes a peptide called MOTS-c, which can directly attack bacteria and reprogram immune cells.
An ancient weapon rediscovered
MOTS-c is a host defense peptide: a small protein chain produced by the body itself to fight pathogens. The peptide has positively charged and hydrophobic domains that allow it to penetrate bacterial membranes, including those of E. coli and MRSA, the antibiotic-resistant bacterium. In a mouse model of severe peritonitis, MOTS-c fully neutralized MRSA infectivity.
The fact that mitochondria can encode something like this is not coincidental. Mitochondria descend from bacteria that were absorbed into cells billions of years ago. They have retained a small genome of their own. The researchers suggest that MOTS-c is a remnant from that bacterial past, now deployed as a weapon for the host.
Immune cells reprogrammed
MOTS-c’s action extends beyond direct bacterial contact. In human monocytes, a type of white blood cell, signals such as interferon-gamma and bacterial cell wall material (lipopolysaccharides) stimulated the production of endogenous MOTS-c. When researchers added extra MOTS-c externally during monocyte development, those cells differentiated into macrophages with a distinct activity profile. These reprogrammed macrophages cleared bacteria more efficiently and showed a shifted metabolism.
From a longevity perspective, this is noteworthy. Aging is accompanied by declining mitochondrial function and a less effective immune system. If MOTS-c indeed bridges these two systems, it could offer a starting point for research into infection resistance in later life. This is still early laboratory research, and whether these effects occur in older humans remains to be investigated.
Want to research this yourself?
Search for example:
- mitochondrial genome immune function | host defense peptide aging | mitochondria-encoded peptide immunomodulation