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.
Share this page. 9/11: How the twin towers were built. The 110-storey landmarks that dominated the Manhattan skyline for nearly 30 years were reduced to rubble in the 9/11 suicide attacks of 2001. Thousands of people in the World Trade Center, and on the planes that crashed into them, lost their lives.