Anatomy & Physiology

Anatomy & Physiology Study Guide IgM, the first type of antibody secreted after an antigen arrives; and (5) IgA, found in glandular secretions. • In humoral immunity, the antibodies first produced by plasma cells are the agents of the primary response. The maximum antibody titer appears during the secondary response to antigen exposure. • The initial steps in the immune responses to viral and bacterial infections differ. • Interleukins increase T cell sensitivity to antigens exposed on macrophage membranes; stimulate B cell activity, plasma cell formation, and antibody production; enhance nonspecific defenses; and moderate the immune response. • Interferons slow the spread of a virus by making the synthesizing cell and its neighbors resistant to viral infections. • Tumor necrosis factors (TNFs) slow tumor growth and kill tumor cells. • Several cytokines adjust the activities of phagocytic cells to coordinate specific and nonspecific defenses. • Colony-stimulating factors (CSFs) are factors produced by active T cells, cells of the monocyte- macrophage group, endothelial cells, and fibrocytes. Immunological competence enables a normal immune response; abnormal responses result in immune disorders: • Immunological competence is the ability to produce an immune response after exposure to an antigen. A developing fetus receives passive immunity from the maternal bloodstream. After delivery, the infant begins developing active immunity following exposure to environmental antigens. • Autoimmune disorders develop when the immune response inappropriately targets normal body cells and tissues. • In an immunodeficiency disease, either the immune system does not develop normally, or the immune response is blocked. • Allergies are inappropriate or excessive immune responses to allergens (antigens that trigger allergic reactions). The four types of allergies are immediate hypersensitivity (Type I), cytotoxic reactions (Type II), complex immune disorders (Type III), and delayed hypersensitivity (Type IV). • In anaphylaxis, a circulating allergen affects mast cells throughout the body. • Interleukin-1 released by active macrophages triggers the release of ACTH by the adenohypophysis. Glucocorticoids produced by the suprarenal cortex moderate the immune response, but their long-term secretion can lower a person’s resistance to disease. The immune response diminishes with advancing age: • For all body systems, the lymphatic system provides defenses against infection and returns tissue fluid to the circulation.

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