In HIT, the immune system forms antibodies against heparin when it is bound to a protein called platelet factor 4 (PF4). These antibodies are usually of the IgG class and their development usually takes about five days.
The first elevator shaft preceded the first elevator by four years. Construction for Peter Cooper's Cooper Union Foundation building in New York began in 1853. An elevator shaft was included in the design, because Cooper was confident that a safe passenger elevator would soon be invented.
According to Gray, what Elisha Otis patented in 1861 (two years after Tufts) was basically a freight elevator typical of the eraâan open platform designed to haul goods up and down. What made it special was his patented safety device at the top. Without safeties, elevators were dangerous.