Table 1.
Hemostasis-relevant platelet receptors and respective ligands in neonates
| Receptor | Ligand | Ligand expression in preterm infants | Ligand expression in term infants | References |
|---|---|---|---|---|
| GPIb | VWF (h) | Increased in preterm; unusually large VWF multimers | Increased | 106,107 |
| Thrombin (h) | See PAR Thrombin below | |||
| P-selectin (m, h, r) | Reduced in fetal platelets and endothelial cells | Normal P-selectin content in unstimulated human samples but reduced surface expression in stimulated platelets | 3,108 | |
| Mac-1 (m, h) | Reduced on fetal neutrophils, related to gestational age | 63,64,109 | ||
| GPIIb | Fibrinogen (h) | Slightly reduced in small-for-gestational-age and extremely premature infants | No difference (slight increase around day 5 postnatal) | 110-113 |
| VWF (h) | See GPIb VWF above | |||
| Vitronectin (h) | Reduced | 114 | ||
| Fibronectin (h) | Reduced | Reduced | 115,116 | |
| GPVI; GPIa/IIa | Collagen (r, h) | Changing collagen types during fetal development | 117-120 | |
| PAR | Thrombin (h) | Thrombin generation similar between preterm and term infants; prothrombin activity below term neonates. | Prothrombin ∼50% of adult values (contradicting results for peak thrombin activity) | 113,121-127 |
| P2Y | ADP (h) | Reduced dense granules and ADP content | 128,129 | |
| Thromboxane receptor | Thromboxane A2 (h) | Reduced platelet release upon collagen stimulation. | Elevated thromboxane levels in plasma; reduced production by washed platelets | 30,130 |
h, human data; m, mouse data; r, rat data.