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.
At the time of the attacks, media reports suggested that tens of thousands might have been killed, as on any given day upwards of 100,000 people could be inside the towers. Estimates of the number of people in the Twin Towers when attacked on September 11, 2001 range between 14,000 and 19,000.