At that time, platelets bore names such as particles, corpuscles, and globules.
Hewson (around 1780) reported undefined blood particles. For instance, van Leewenhoek, the Dutch microscopist who delivered amazing, seminal observations of natural life, reported precise observations of platelets around 1675. Prior to Bizzozzero, and indeed as early as the seventeenth century, platelets had been suspected. This Italian (Lombardy) physician and researcher also very elegantly acknowledged the role of platelets not only in hemostasis but also in thrombosis. Was Boyle (end of the seventeenth century), Donné (early nineteenth century), or Bizzozzero (end of the nineteenth century) the real discoverer? It is generally considered that the acknowledgment there is a third cellular element in blood besides, and independent of, erythrocytes and leukocytes, is attributed to Bizzozzero, around 1881–1882. The initial discovery of platelets is disputed. In combination, these properties argue in favor of allowing platelets the title of immune cells.ĭiscovery of Platelets and Their Functions The question has also arisen as to whether platelets can present antigen via their abundantly expressed MHC class I molecules. However, platelets can use a complete signalosome (apart from the last transcription step, though it is likely that this step can be circumvented by retrotranscribing RNA messages).
#Platelets are cell fragments. license#
Does assistance to immune cells itself suffice to license a cell as an “immune cell”? Platelets prove capable of sensing different types of signals and organizing an appropriate response. Platelets have now entered the field of immunity as inflammatory cells. This view prevailed until it became evident that platelets play a role in homeostasis and interact with cells other than with vascular endothelial cells then began the era of physiological and also pathological inflammation. Actually, platelets possess almost every characteristic of cells, apart from being capable of organizing their genes: they have neither a nucleus nor genes. Some gladly categorized platelets as cells but they were certainly not fully licensed as such for cell physiologists. As early as 1930s, platelets entered the arsenal of medicines were transfused, and were soon manipulated to become a kind of glue to repair damaged tissues. The enlightened face showed that besides hemostasis, platelets contained factors involved in healing. As such, however, they were acknowledged as immunizing (to specific HPA and HLA markers): the platelet’s dark face. For long, platelets have been considered sticky assistants of hemostasis and pollutants of blood or tissue samples they were just cell fragments. Wright, at the beginning of the twentieth century, identified their bone-marrow origin. Small fragments circulating in the blood were formally identified by the end of the nineteenth century, and it was suggested that they assisted coagulation via interactions with vessel endothelia.
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