Second Line Of Defense

The first line of defense is comprised of two barriers, the physical and chemical barriers. These barriers or blockades are always ready and prepared to defend the body from infection. The first barrier is the physical blockade between the inside of the body and the outer world. Physical blockades of the first defense system includes the skin, tears, and the stomach. After the outer line of defense is breached, the body starts it innate immune system to help prepare to take action on the foreign infectious disease or bacteria. The chemical barrier or the innate immunity is made up of a collection of white blood cells along with groups of chemical messengers. Innate immunity is activated by a set of molecules that are found only on invading
This defense system is non-specific and non-adaptive. In the second line there are many cells involved such as leukocytes, neutrophils, T helper cells, cytotoxic T-cells, macrophages, dendritic cells, B-cells, and suppressor T-cells. The phagocytes or neutrophil squeeze through the capillary wall and into the infected tissue to engulf and digest offending
The two cells have different responses, the T-cells are involved in a cell-mediated response, while the B-cell are involved in the humoral response. During the process of the T-cell response there are many different variations of the T-cell such as the killer T-cell, helper T-cells, suppressor T-cells, and memory cells. By using cytotoxic T-cell, the third response is able to detect and recognize antigens on the surface of infected cell. The cytotoxic T-cells then bind to the infected cells secrete cytotoxins that induce apoptosis in the infected cell and perforins that cause perforations in the infected cells. When both of these mechanisms are through they will help destroy pathogens in the infected body. This diagram will help with the visualization of these mechanism and their processes. Killer T-cells combine with antigens on the surface of any invading cell and release a powerful group of chemicals called lymphokines. Some lymphokines kill the pathogens directly, others stimulate lymphocytes to become active and help increase the inflammation so that there are more macrophages. Helper T-cells co-operate with B-cells in the antibody production. They also activate macrophages and promote inflammation. Memory cells remain even after the pathogens have been killed to stop