Self-extinguishing relay waves enable homeostatic control of human neutrophil swarming

Neutrophils collectively migrate to sites of injury and infection. How these swarms are coordinated to ensure the proper level of recruitment is unknown. Using an ex vivo model of infection, we show that human neutrophil swarming is organized by multiple pulsatile chemoattractant waves. These waves propagate through active relay in which stimulated neutrophils trigger their neighbors to release additional swarming cues. Unlike canonical active relays, we find these waves to be self-terminating, limiting the spatial range of cell recruitment. We identify an NADPH-oxidase-based negative feedback loop that is needed for this self-terminating behavior. We observe near-constant levels of neutrophil recruitment over a wide range of starting conditions, revealing surprising robustness in the swarming process. This homeostatic control is achieved by larger and more numerous swarming waves at lower cell densities. We link defective wave termination to a broken recruitment homeostat in the contex..., Neutrophil Isolation Protocol:
Imaging media was first prepared with RPMI (w/o Phenol Red, 25mM HEPES, L-Glutamate) and 0.4% Human Serum Albumin (HSA) (Sigma Cat: A5843). HSA was added directly to RPMI and then centrifuged at 500xg for 5 min until fully dissolved. The mix was then filtered with a .22 μm Steriflip filter (Millipore Sigma: SE1M179M6) before further use. Imaging media was always prepared fresh on the same day of imaging.
Blood specimens from patients were obtained with informed consent according to the institutional review board-approved study protocol at the University of California - San Francisco (Study #21-35147). Fresh samples of peripheral blood (2 tubes, 7 mL each) from healthy adult volunteers were collected via a BD 23-gauge butterfly needle collection set (SKU: 23-021-022) into 10 ml BD Vacutainer EDTA tubes (SKU:366643). Volunteers were informed not to take ibuprofen, acetaminophen, or more than one drink of alcohol within 24 hrs, class 1 or 2 antihistamines wi..., , # Data from: Self-extinguishing relay waves enable homeostatic control of human neutrophil swarming

[https://doi.org/10.5061/dryad.k0p2ngfg2](https://doi.org/10.5061/dryad.k0p2ngfg2)

Neutrophils collectively migrate to sites of injury and infection. How these swarms are coordinated to ensure the proper level of recruitment is unknown. Using an *ex vivo* model of infection, we show that human neutrophil swarming is organized by multiple pulsatile chemoattractant waves. These waves propagate through active relay in which stimulated neutrophils trigger their neighbors to release additional swarming cues. Unlike canonical active relays, we find these waves to be self-terminating, limiting the spatial range of cell recruitment. We identify an NADPH-oxidase-based negative feedback loop that is needed for this self-terminating behavior. We observe near-constant levels of neutrophil recruitment over a wide range of starting conditions, revealing surprising robustness in the swarming process. ...