Focus on the ‘Sentinel’ cells of the immune system
Young dendritic cells are smooth customers. When fluid blocks their passage (hydraulic resistance), they swallow it up before spitting it back out behind them. This phenomenon is called macropinocytosis and allows them to travel into the furthest-flung corners of the organism. And that is their ultimate objective. These immune system cells trawl through the epithelial tissues that serve as an interface between our bodies and the outside world: skin, lungs, intestines, etc.
Known as the ‘sentinels’ of the organism, they capture all foreign or suspect molecules and carry them to the lymph nodes. As they mature, dendritic cells lose their macropinocytosis abilities. This leads them to abandon their patrol and quickly migrate to the lymph nodes. Once there, they transmit information to all the molecules they encountered on their first trip and introduce them to other immune system cells, which depending on the information gleaned, may attack these intruders.
Over and above providing us with fundamental knowledge, these findings may be useful in the fight against cancer. We know that some cancerous cells are also capable of macropinocytosis, and use it as fuel by absorbing their surroundings. These cells could therefore also use it to get around and invade healthy tissue, or to enter the blood stream and colonize other organs to form metastases. Although it seems far off yet, Hélène Moreau is hopeful that one day there may be a way of modulating this macropinocytosis or the cell environment’s hydraulic resistance to slow down tumor progression.