Certain immune cells betray their cellular colleagues during allergic reactions. Mast cells, the security forces of the immune system, can initiate allergic inflammation when they encounter unfamiliar proteins (SN: 9/5/07). For the first time, researchers have observed these overactive cells attracting and capturing other crucial immune cells, then releasing their captives’ inflammatory chemicals in a process called nexocytosis. This discovery could aid scientists in understanding the underlying causes of health issues involving allergies or the immune system, such as asthma and dermatitis.
When mast cells detect proteins from outside the body, they trigger an inflammatory response by releasing granules, which are packages of chemicals that attract other immune cells—including neutrophils, a vital type of white blood cell (SN: 9/23/24). Curious about the interaction between mast cells and neutrophils, immunologist and biochemist Michael Mihlan and his team induced mast cells to react to a human blood protein. They then observed the reactions in both mouse and human cells under a microscope. The researchers reported in the Sept. 19 issue of Cell that mast cells attracted neutrophils toward them and then engulfed these specialized white blood cells. “This was a complete surprise to us,” says Mihlan, from the University of Münster in Germany.
Even after the trapped neutrophils died, their proteins, DNA, and other molecules remained inside the mast cells. These mast cells could then use these remnants to sustain themselves or perform nexocytosis by releasing inflammatory neutrophil chemicals along with granules when another allergic reaction occurred. In the future, Mihlan hopes to determine whether mast cells’ trapping strategy can be beneficial in certain situations, such as defending against foreign bacteria.
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