Summary Siglecs are cell surface lectins that recognize sialic acids and are primarily expressed in hematopoietic cells. Previous studies showed that some Siglecs regulate macrophage function. In the present study, we examined the induction and putative roles of mouse Siglec‐F in bone‐marrow‐derived macrophages in mice. A quantitative RT‐PCR analysis showed that the basal expression of Siglec‐F was weak in bone‐marrow‐derived macrophages differentiated by macrophage colony‐stimulating factor. However, a 24‐hr stimulation with granulocyte–macrophage colony‐stimulating factor (GM‐CSF) enhanced Siglec‐F expression. GM‐CSF also enhanced Siglec‐F expression in thioglycollate‐induced peritoneal macrophages. The inhibition of signal transducer and activator of transcription 5 (STAT5), but not that of phosphoinositide 3‐kinase or mitogen‐activated protein kinase kinase, significantly reduced the induction of Siglec‐F. Interleukin‐3, which uses a common β‐chain shared with the GM‐CSF receptor to stimulate the STAT5 pathway, also enhanced Siglec‐F expression. The knockdown of Siglec‐F by a specific small interfering RNA enhanced GM‐CSF‐induced STAT5 phosphorylation, suggesting that Siglec‐F down‐regulates its own expression upon prolonged GM‐CSF stimulation. Furthermore, the knockdown of Siglec‐F reduced the STAT6 phosphorylation and expression of arginase‐1 in interleukin‐4‐stimulated macrophages. These results suggest that Siglec‐F fine‐tunes the immune responses of macrophages.

The vortex rings generated in non-circular jets are deformed and interacted three-dimensionally owing to self-induced velocity, and the vortex motion enhances mixing. To understand the mechanism of the mixing enhancement, it is crucial to make clear the three-dimensional vortical structure caused by the interaction of non-circular vortices. In the present study, the details of three-dimensional vortical structure of a rectangular jet of aspect ratio 4 is clarified using Large Eddy Simulation (LES), and the interaction mechanism of rectangular vortices is discussed, focusing the deformation of vortices. The simulation results reveal the details of the vortex interaction in the rectangular jet: the vortices deform owing to the non-uniform curvature effect, and the interaction of vortices generates hairpin vortices via vortex stretching.

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