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.
On September 11, 2001, New York City suffered the deadliest terrorist attack in the history of the United States when a group of terrorists crashed two hijacked jets into the cityâs tallest buildings: the twin towers of the World Trade Center. The buildings were destroyed and nearly 3,000 people were killed.