secretory cell platelet A non-nucleated disk-shaped cell formed by extrusion from megakaryocytes, found in the blood of all mammals, and mainly involved in blood coagulation. Platelets are reportedly CCR1-positive, CCR2-negative, CCR3-positive, CCR4-positive, CCR5-negative, CCR6-negative, CCR7-negative, CCR8-negative, CCR9-negative, CCR10-negative, CD16-positive, CD23-positive, CD32-positive, CD40-positive, CD41-positive CD42-positive, CD61-positive, CD62P-positive, CD64-positive, CD89-positive, CD102-positive, CD147-positive (activated platelets), CD154-positive (activated platelets), CD162-positive, CD209, CD282-positive, CD284-positive, CD289-positive, CD181-negative, CD182-negative, CD183-negative, CD184-positive, CLEC2-positive, GPVI-positive, JAMC-positive, PAR1-positive, PAR2-negative, PAR3-positive, PAR4-positive, TSP1-positive, and TXA2R-positive. Platelets can reportedly produce CCL2, CCL3, CCL5, CCL7, CCL17, CD40L, CXCL1, CXCL4, CXCL4L1, CXCL5, CXCL7, CXCL8, CXCL12, EGF, factor V, factor VII, factor XI, factor XIII, bFGF, histamine, IGF-1, IL-1beta, PAI-1, PDGF, plasminogen, protein S, serotonin, TGF-beta, TFPI, VEGF, and vWF. A non-nucleated disk-shaped cell formed by extrusion from megakaryocytes, found in the blood of all mammals, and mainly involved in blood coagulation.