Researchers at the Medical Research Council Laboratory of Molecular Biology have described for the first time how cells can digest bacteria and viruses from within, identifying a newly named germ-resistance pathway called antibody-directed xenophagy, or ADX. The findings, published on 4 June 2026 in the Cell Press journal Molecular Cell, point to a mechanism that could eventually shape future treatments for infections.
A new layer of immune defence
The study shows that cells are not limited to defending themselves from invaders in the bloodstream. Instead, when antibody-coated pathogens cross the cell membrane, they can be recognized and targeted for destruction inside the cell. The research team said they observed this process in connection with both Salmonella and adenoviruses.
According to the report, the pathway starts with a specialised protein called TRIM21. Once an antibody-labeled pathogen enters a cell, TRIM21 flags it with ubiquitin, a marker that signals the cell has been invaded. That tag then helps trigger the breakdown of the pathogen through autophagy.
Why the finding matters
The authors say the immune effect appears broad, because the same mechanism can mark and destroy both adenoviruses and Salmonella from infected cells. They also reported that the system was tested across a range of human cell lines and, in the case of Salmonella, in living mouse models, suggesting the immunity is likely widespread throughout the body.
Leo James, a group leader at the MRC LMB, said the work moves from discovery to mechanism to physiological importance in a single study. The team notes that without TRIM21, a significant component of protective immunity in vivo against viruses is lost, underlining the protein’s role in the body’s defence system.
Potential implications for future therapies
The researchers say the ADX pathway could have future medical applications, although much more research is still needed before any treatment becomes reality. They suggest that antibody or small-molecule therapeutics might one day be used to mark pathogens in the blood so TRIM21 can recognise them quickly once they enter cells.
For now, the finding adds a new dimension to understanding how the immune system works. Rather than acting only as a back-up response, the pathway may represent an important primary mode of protective immunity, with the possibility that other ADX-stimulating proteins still remain to be discovered.
Read more from the original report at the UKRI news page.
