McKenna's Pharmacology for Nursing, 2e

C H A P T E R 1 5  Introduction to the immune response and inflammation 233

would start to leak out of the capillaries (often this can be heard as rales); the person would complain of chest discomfort; and the increased blood flow to the area of infection would make it appear hot or very active on a scan. No matter what the cause of the insult, the body’s local response is the same. Once the inflammatory response is under way and neutrophils become active, engulfing and digesting injured cells or the invader, they release a chemical that is a natural pyrogen , or fever-causing substance. This pyrogen resets specific neurons in the hypothalamus to maintain a higher body temperature, seen clinically as a fever. The higher temperature acts as a catalyst to many of the body’s chemical reactions, making the inflam­ matory and immune responses more effective. Treating fevers remains a controversial subject because lowering a fever decreases the efficiency of the immune and inflam­ matory responses. The leukotrienes (autocoids activated through the kinin system) affect the brain to induce slow-wave sleep, which is believed to be an important energy con­ servation measure for fighting the invader. They also cause myalgia and arthralgia (muscle and joint pain)— common signs and symptoms of various inflammatory diseases—which also cause reduced activity and save energy. All of these chemical responses make up the total clinical picture of an inflammatory reaction. The immune response More specific invasion can stimulate a more specific response through the immune system. As mentioned previously, stem cells in the bone marrow produce lymphocytes that can develop into T lymphocytes (so named because they migrate from the bone marrow to the thymus gland for activation and maturation) or B lymphocytes (so named because they are activated in the bursa of Fabricius in chickens, although the specific point of activation in humans has not been identified). Other identified lymphocytes include natural killer cells and lymphokine-activated killer cells. Both of these cells are aggressive against neoplastic or cancer cells and promote rapid cellular death. They do not seem to be programmed for specific identification of cells. Nutritional: Immune: Immune response

Research in the area of lymphocyte identification is relatively new and continues to grow. There may be other lymphocytes with particular roles in the immune response that have not yet been identified. T cells T cells are programmed in the thymus gland and provide what is called cell-mediated immunity (Figure 15.3). T cells develop into at least three different cell types. 1. Effector or cytotoxic T cells are found throughout the body. These T cells are aggressive against non-self cells, releasing cytokines, or chemicals, that can either directly destroy a foreign cell or mark it for aggressive destruction by phagocytes in the area via an inflammatory response. These non-self cells have membrane-identifying antigens that are different from those established by the person’s MHC. They may be the body’s own cells that have been invaded by a virus, which changes the cell membrane; neoplastic cancer cells; or transplanted foreign cells. 2. Helper T cells respond to the chemical indicators of immune activity and stimulate other lymphocytes, including B cells, to be more aggressive and responsive. 3. Suppressor T cells respond to rising levels of chemicals associated with an immune response to suppress or slow the reaction. The balance of the helper and suppressor T cells allows for a rapid response to body injury or invasion by pathogens, which may destroy foreign antigens immediately and then be followed by a slowing reaction if the invasion continues. This slowing allows the body to conserve energy and the components of the immune and inflammatory reaction necessary for basic protection and to prevent cellular destruction from a continued inflammatory reaction. B cells B cells are found throughout the MPS in groups called clones. B cells are programmed to identify specific proteins or antigens. They provide what is called humoral immunity (Figure 15.4). When a B cell reacts with its specific antigen, it changes to become a plasma cell. Plasma cells produce antibodies , or immunoglobulins, which circulate in the body and react with this specific antigen when it is encountered. This is a direct chemical reaction. When the antigen and antibody react, they

Stimulated by helper T cells Inhibited by suppressor T cells

NON-SELF CELL

Cytotoxic T cell

Release of cytokines

Memory cytotoxic T cells

FIGURE 15.3  Cell-mediated immune response. Cytotoxic T cells are activated when recognising a non-self cell. Memory T cells are formed. Cytokines are released to destroy the non-self cell.

Death of non-self cell