Neutrophils choose the right direction

Two distinct signaling pathways operate sequentially, thus guiding neutrophils to bacterial invaders, according to Heit et al. on page 91. Although one pathway lures neutrophils in the right general direction, the other pathway dominates when the prey is within reach.

Neutrophils leave the bloodstream and migrate to infection sites by following intermediary chemokine signals (such as IL-8) that are generated by damaged host cells. End-target signals like fMLP or LPS, either released by the pathogen itself or by the body in response to the bacteria, also attract neutrophils. Since the blood cells prefer to pursue end-targets when both signals are present, the authors speculated, correctly, that different pathways controlled the two responses.

The pathways can be distinguished by their kinase-dependence. Migration to intermediary chemoattractants depended on PI3K, which phosphorylated Akt. End-targets induced migration...