The secondary response involves mainly memory cells, this is the response that occurs on the second entrance of a microorganism or virus that has been encountered before and dealt with by the primary response.he primary immune system is also called innate immunity or auxiliary immunity because it is unspecific and present in everyone. These include physical and chemical barriers t â¦ hat protect the body from many different microscopic organisms. --Skin (and hair) acts as a large physical barrier.
The twin towers of the World Trade Center (WTC) collapsed on September 11, 2001, as a result of being struck by jet airliners hijacked by terrorists affiliated with al-Qaeda during the September 11 attacks.
But the real carnage was concealed for now by the twisted, smoking, ash-choked carcasses of the twin towers, in which thousands of people used to work on a weekday. The collapse of the towers caused another World Trade Center building to fall 10 hours later, and several other buildings in the area were damaged or aflame.