Neutrophil breaching of the blood vessel pericyte layer during diapedesis requires mast cell-derived IL-17A.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and basic mechanistic imaging study without human clinical data.
PubMed 36396641 · doi:10.1038/s41467-022-34695-7
What was done
Researchers used confocal intravital microscopy to observe neutrophil behavior in the sub-endothelial space of inflamed venules. They examined the role of perivascular mast cells and IL-17A in neutrophil extravasation by comparing normal conditions against mast cell-deficient models as well as genetic and pharmacological blockade of IL-17A. They also evaluated downstream effector expression (ICAM-1 and CXCL1) in pericytes.
What was found
Neutrophils demonstrated directed abluminal movement along pericyte processes toward perivascular mast cells, forming specific extravasation hotspots. Mast cell deficiency or IL-17A inhibition resulted in impaired sub-endothelial migration and reduced neutrophil breaching of the pericyte layer. Perivascular mast cells were shown to supply IL-17A, which induced the local enrichment of ICAM-1 and CXCL1 in nearby pericytes. The abstract reports qualitative directions and mechanisms but provides no specific numerical values.
Why it matters
The study defines a previously unrecognized mast cell-IL-17A-pericyte signaling axis that governs the terminal exit of neutrophils across the blood vessel wall. This identifies potential mechanistic targets for intervening in excessive neutrophil-driven inflammatory conditions.
Limits
The work is entirely preclinical and mechanistic; clinical translatability in human vascular beds remains to be established. The abstract does not disclose sample sizes, specific animal models, statistical effect sizes, or quantitative data.
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