The Body 's Defence Against Infectious Disease

The immune system is made up of several types of cells that work together to fight infections. Lymph cells (called lymphocytes) are the main type of cell in the adaptive immune system. There are 2 types of lymph cells: T cells and B cells. When B cells respond to an infection, they change into plasma cells. The plasma cells are found mainly in the bone marrow—the soft, inner part of some bones. The plasma cells

The immune system depends on the body’s structures to help it function. For instance, the skin acts as the “body’s first line of defense.” If a pathogen finds a breach in the skin barrier, it is the circulatory system that must now signal the immune system of the invader. Shortly after, white blood cells will be notified of the infection and will target and destroy the pathogen.

One defence mechanism of the human body is that when a person gets ill or is infected the person will get a fever, this is a method of notifying the person. This is a bodily defence mechanism produced by the immune system, its main purpose is to make it difficult for the virus to multiply prepare for the virus. The body’s pH level will also change to make it less optimal for the virus. The immune system’s mechanism will change depending on the body’s condition. If the body gets cut the immune system will causes inflammation, this will cause red blood cells to come to the

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. Adaptive immunity refers to antigen-specific immune response.

The body’s protection against viruses, bacteria and other types of invasions is our immune system (Tortora, 2014).

a. This function is mediated by T cells and B cells (memory cells) in our body via adaptive immunity. The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is “remembered” by a signature antigen. The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by memory cells. Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. So basically killer T cells will identify antigens present on foreign cells. These antigens are not found in any of the cells inside our body. Therefore, T cells will identify them and kill them.

Defense mechanisms are said to be specific because depending on which one they focus on one specific part of the body or a specific type of pathogen.

Adaptive immunity (p.446): The body’s ability to recognize and defend itself against distinct invaders and their products.

The immune system is made up of trillions of specialised cells (white blood cells) that detect and destroy pathogens or their toxins. Some white blood cells, which are

The organs that make up the lymphatic and immune system are the tonsils, spleen, thymus gland, lymph nodes, and lymphatic vessels. White blood cells (leukocytes), red blood cells (erythrocytes), plasma, and platelets (thrombocytes) make up the blood. Lymphocytes are leukocytes (white blood cells) that help the body fight off diseases. Two types of lymphocytes are B cells and T cells. Lymphocytes recognize antigens, or foreign substances/matter, in the body. Lymphocytes are a classification of agranulocytes, or cells (-cytes) without (a-) granules (granul/o) in the cytoplasm. B cells are created from stem cells, which are located in the bone marrow. B cells respond to antigens by becoming plasma cells. These plasma cells then create antibodies. Memory B cells produce a stronger response with the next exposure to the antigen. B cells fight off infection and bacteria while T cells defend against viruses and cancer cells. A hormone created by the thymus gland called thymosin changes lymphocytes into T cells. The thymus gland is active when you are a child and slowly shrinks, as you get older. T cells bind to the antigens on the cells and directly attack them. T cells secrete lymphokines that increase T cell production and directly kill cells with antigens. There are three types of T cells: cytotoxic T cells, helper T cells, and memory T cells.

The lymphatic system are a complex network of specialised cells and organs that defend the body against infection. Lymphatic organs include the bone marrow, spleen, thymus gland, lymph nodes, tonsils, adenoids, appendix and clumps of tissue in the small bowel. A function of the lymphatic system is to nurture and mature the B and T-lymphocytes (white blood cells vital to immune function). Cancerous changes can take place

Adaptive, or acquired, immunity refers to antigen-specific defence mechanisms that take several days to become protective and are designed to react with and remove a specific antigen. This is immunity develops throughout life.

The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by "memory cells". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. so basically killer T cells will identify antigens present on foreign cells. These antigens are not found in any of the cells inside our body. So T cells will identify them and kill them.

The immune system is comprised of two responses: the adaptive immune response and the innate immune response. The first line of defence against invading organisms is classified as the innate immune response and the second line of defence and protection against re- exposure to the same pathogen is known as the adaptive immune response.

Another type of cells that protect your body is the Phagocytes. Phagocytes are types of white blood cells that directly ingest the harmful pathogens through the process of phagocytosis. They bind to the pathogen and engulf it. When it engulfs the pathogen, Phagocytes keep the antigen so it can be presented to cells to make antibodies. (Kidshealth.org)