An important defense against disease in vertebrate animals is the ability to eliminate, inactivate, or destroy foreign substances and organisms. Explain how the immune system achieves all the following.
1) Provides an immediate nonspecific immune response
2) Activates T and B cells in response to an infection
3) Responds to a later exposure to the same infectious agent
4) Distinguishes self from nonself
__________________________________________________________
1) First, our bodies have physical barriers, such as skin and clots, to protect us against pathogens. Saliva, mucous, vomiting, and diarrhea help to partially get rid of anything harmful that has entered our bodies. Chemical barriers such as salts and acids also help to breakdown harmful, foreign substances. Inflammatory responses (the dilation of blood vessels) help stimulate fever and changing body temperature to increasing clotting and white blood cells production. Cell interferons from infected cells provide stimulation for production of chemicals for inhibition of viral reproduction.
2) White blood cells begin to "eat" the pathogens and display the antigens on the body of the macrophages, signaling for T and B cells. The antigen activates and helper T cells. The antigen binds to B cells and activates B cells. The helper T cells then activates the B cell and/or cytotoxic T cells. It is Interleukin 1 from the macrophages that activate helper T cells and Interleukin 2 and cytokines from helper T cells activate B cells or cytotoxic T cells. T cells either become memory T cells or killer T cells. Memory T cells take note of the pathogen and store that in the blood so that if the same pathogen entered the body again, the body will be able to recognize it. The killer T cells are the ones that go and destroy the pathogen. The B cells can either become memory B cells, which function like memory T cells, or they can become plasma B cells that that produce antibodies that can attach on to and weaken the antigens of a pathogen.
3) As discussing in number 2, memory T and B cells stored information for recognition of pathogens in the blood stream. Each memory cell is specific to the same previously encountered antigen. Since the body has previously had to fight against the recognized antigen, the memory cells have greater power against the antigen and and are able to respond faster and to a greater extent. Therefore, secondary immune response is stronger due to increased strength and concentration of memory cells and due to complex cytokines.
4) Each cell has a unique marker such as specific proteins, cytokines, glycoproteins, etc. In bone marrow and in the thymus, antigen receptors are tested and the binding stimulates an immune response. There self-antigen receptors are eliminated or inactivated.
