Week_12_-_Basic_review_of_the_immune_sys - Week 12 Basic...

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Week 12 - Basic review of the immune system The role of the immune system is to protect the body against invaders, such as bacteria and viruses, as well as any “home-grown” threats to the body, such as malignant cells. When the immune system is exposed to toxicants, the ability of the body to defend itself and maintain normal function can be seriously compromised. The immune system is comprised of a complex series of cells and tissues that is too extensive to delve into in any great detail in this lecture. Instead, this lecture will provide a brief description of the immune system structure and function; an overview of how the immune system responds to toxicants; and an introduction to basic methods used to study immunotoxicology. Acquired vs. innate immunity The immune system can be divided into two types of immunity: innate and acquired. Innate immunity is a non-specific immune response that will indiscriminately attack invaders regardless of their nature. Innate immunity has no memory, which means that repeated exposures to the same pathogen will produce the same response as the first exposure to the pathogen. Acquired immunity , on the other hand, involves immune responses that are specific to the invading pathogen, and it does have a memory, such that repeated exposure to the same pathogen will produce an enhanced response to that same pathogen the next time it is encountered. Structure of the immune system Unlike organs like the liver and heart, which are localized masses of tissue, the immune system is comprised of both tissues and cells throughout the body. The tissues are organized into primary lymphoid tissues , such as the bone marrow and thymus, that contain lymphoid progenitor cells and are involved in lymphoid cell production and development; and secondary lymphoid tissues, such as the spleen and lymph nodes, which play a role in lymphocyte homing, antigen presentation and acquired immune response. The bone marrow contains pluripotent hematopoietic stem cells that are the source of most cells in the immune system. The thymus plays a later role in immune system development, in that T cells produced in the bone marrow must travel to the thymus to complete their development.
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Source: McGraw Hill (used with permission) The components of the immune system can be divided into two categories: cellular and humoral. The cellular component relies on direct contact between the immune cell(s) and the pathogen, while the humoral component is an antibody -mediated response that
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Week_12_-_Basic_review_of_the_immune_sys - Week 12 Basic...

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