During an allergic response, some immune cells digest others

Certain immune cells backstab their cellular coworkers at some stage in allergic reactions.

Mast cells, the safety patrols of the immune system, can trigger allergic inflammation once they run into unfamiliar proteins (SN: 9/5/07). For the first time, researchers have seen these overeager cells attract and trap other key immune cells, then expel their hostages’ inflammatory chemicals in a process dubbed nexocytosis. The invention may assist scientists take note the root causes of medical conditions involving allergic reactions or the immune system, comparable to asthma and dermatitis.

When mast cells sense proteins from outside the body, they instigate an inflammatory response by expelling granules, packages of chemicals that attract other immune cells — including neutrophils, a key sort of white blood cell (SN: 9/23/24).

Hooked in to how mast cells and neutrophils engage, immunologist and biochemist Michael Mihlan and colleagues triggered mast cells to react to a human blood protein. The team then watched the reactions in both mouse and human cells through a microscope. Mast cells lured neutrophils toward them, then swallowed the really expert white blood cells, the researchers reported within the Sept. 19 Cell. “This used to be a complete surprise to us,” says Mihlan, of the University of Münster in Germany.

Even after trapped neutrophils died, their proteins, DNA and other molecules remained inside their mast cell captors. The mast cells may then use these leftovers to sustain themselves. Or, they'll perform nexocytosis by spewing out inflammatory neutrophil chemicals alongside granules when the other allergic reaction began.

Someday, Mihlan hopes to learn whether mast cells’ trapping strategy is a force for good in some cases, comparable to struggling with off foreign bacteria.