Where is Waldo? or find the platelet.

Platelets evolved from nucleated thrombocytes that exhibit both coagulation and immune function. The essential role of platelets in coagulation is common knowledge. The larger and critical role of platelets in immune responses and cancer are frequently overlooked in our modern-day, large-data-set, sequencing-oriented efforts. Much like Waldo, their small size, biophysical characteristics, rapid biological responses, active cytoskeleton, migration capacity, and lack of a nucleus make them difficult to track as single platelets disappear while executing their function into the histologic "tissue scape". The adaptive evolution of platelets is linked to placentalization and stopping massive blood loss. This resulted in exclusion of any platelet nucleus and therefore sustainable gene expression due to being extruded in the billions (1011) per day from megakaryocytes under bone marrow protection. The platelets' small size and sheer number in circulation, combined with an active open canalicular exchange- and membrane-reserve system, plus an array of pathogen receptors enable them to deal with small pathogenic viral treats and to decorate larger ones for further immune identification and immune-cell recruitment. Once stimulated, platelets release most serum-based cytokines and growth factors that contribute to cell growth and wound repair, and potentially to immune suppression. From a self-taught practitioner of the illustrative arts with a ken for platelet biology, this offering is a humble attempt to provide a stimulating sketch of the critical importance of platelet biology and insights into potential new directions for finding the Waldo-esque platelet.