"What intrigued us was that this themeB cells behaving like monocyteshad been seen before in fish and in vitro. But now we have a living example in a mammalian system, where this kind of bipotentiality is realized," said Prof. Gommerman.
This B-cell plasticity provides a potential explanation how cells dedicated to controlling pathogens can respond to a large burden of harmful bacteria without damaging beneficial bacteria and other cells essential for proper function of the intestine.
It also may explain how scientists had failed to appreciate the multi-functionality of some B cells. "There are classical markers immunologists use to identify B cellsreceptors that are displayed on their surfaceand most of them are absent from plasma cells," said Prof. Gommerman. "So in some cases, what people thought was a monocyte could have been a plasma cell because it had changed its surface identity, although monocytes play an important role in innate immunity as well."
This transformational ability, the researchers also found, is dependent on bacteria called commensal microflora that digests food and provides nutrients. That relationship highlights the importance of the gut in fighting infection, and begs the question of whether plasma cells trained in the gut to secrete specific anti-microbial molecules can play a role in other infectious disease scenarios, such as food-borne listeria infection.
It also opens a line of investigation into whether a systemic relationship exists between those anti-microbial molecules and healthy cells in sites remote from the intestine. Understanding the nature of that relationship could improve understanding of inflammatory mechanisms in autoimmune disorders such as lupus, rheumatoid arthritis and mu
|Contact: Jim Oldfield|
University of Toronto