CD4 + FoxP3 + regulatory T cells (CD4 + Tregs) are known to dampen inflammation following severe trauma. Platelets were shown to augment their posttraumatic activation in burn injury, but the exact mechanisms remain unclear. We hypothesized that platelet activation mechanisms via GPIIb/IIIa, fibrinogen, and PAR4 have an immunological effect and modulate CD4 + Treg activation early after trauma. Therefore, C57Bl/6 N mice were i...