Platelets play important roles in the late phase of the immediate hypersensitivity reaction

Platelets have a role in most inflammatory reactions including in the immediate hypersensitivity reaction (IHR) in skin.


Megakaryocyte. Platelets, or thrombocytes, are small, irregularly shaped anuclear cells, which are derived from fragmentation of precursor megakaryocytes. Image source: Wikipedia, GNU Free Documentation License.

Sensitized mice developed biphasic responses characterized by early-phase and late-phase reactions (LPRs). The early phase reaction was not suppressed at 1 hour, but platelet depletion significantly reduced the LPR at 24 hours. Systemic administration of antiplatelet compounds also suppressed the LPR significantly.

These results show that platelets play important roles in the LPR of the IHR in skin by forming platelet-leukocyte complexes via P-selectin in blood and secreting several chemokines that attract leukocytes to skin.


P-selectin is a cell adhesion molecule (CAM) found in granules in endothelial cells and activated platelets. Image source: Wikipedia, GNU Free Documentation License.

References:
Platelets play important roles in the late phase of the immediate hypersensitivity reaction. Risa Tamagawa-Mineoka et al. JACI, Volume 123, Issue 3, Pages 581-587.e9 (March 2009)
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