Immunity (Asthma & Allergies) Flashcards
Hematopoietic and immune blood cells
Originate in bone marrow in stem cells. Often called pluripotent stem cells because they are capable of becoming different types of cells.
Cytokines
Diverse substances produced mainly by bone marrow and white blood cells. They regulate many cellular activities by acting as chemical messengers among cells and as growth factors for blood cells. They act by binding to receptors on target cells.
Interferons
They interfere with the ability of viruses in infected cells to replicate and spread to uninfected cells. They also inhibit reproduction and growth of other cells, including tumor cells, and activate natural killer cells.
Body’s primary external defense mechanism
Intact skin which prevents entry of foreign substances and produces secretions that inhibit microbial growth.
Internal defense mechanisms
Mucous membranes lining the GI and respiratory tracts. Act as physical barriers and produce mucus that trap foreign substances so they may be expelled from the body.
Causes of cellular injury
Chemicals, hypoxia, ischemia, microorganisms, excessive heat or cold, radiation, and nutritional deficiencies or excesses
Cellular response to injury
Inflammation, a generalized reaction to any tissue damage. Attempts to remove the damaging agent and repair the damaged tissue.
Hemodynamic aspect of inflammation
Includes vasodilation, which increases blood supply to the injured area, and increased capillary permeability, which allows fluid to leak into tissue spaces.
Cellular aspect of inflammation
Movement of white blood cells into the area of injury. WBCs are attracted to the injured area by bacteria, tissue debris, plasma protein fractions (complement), and other substances in a process called chemotaxis. After they reach te area, they phagocytize causative agents and tissue debris.
Body’s final defense mechanism
Immune response. An effective response involves lymphoid cells, inflammatory cells, and hematopoietic cells. The immune response stimulates production of antibodies and activated lymphocytes to destroy foreign invaders and mutant body cells.
Immune system
Detects and eliminates foreign substances that may cause tissue injury or disease. Also regulates tissue homeostasis and repair as cells of the immune system identify and remove injured, damaged, dead, or malignant cells.
Major histocompatibility complex (MHC)
Markers that are essential to immune system function because they regulate the antigens to which a person responds and allow immune cells to recognize and communicate with each other. Non-self or foreign antigens are also recognized by distinctive molecules, called epitopes, on their surfaces.
Types of immunity
Innate/natural immunity (not produced by the immune system) includes the general protective mechanisms of the body.
Adaptive/acquired immunity develops during gestation or after birth and may be active or passive. Active immunity is produced by the person’s own immune system in response to a disease caused by a specific antigen or administration of an antigen (a vaccine) from a source outside the body. Duration of active immunity may be brief or it may last for years or a lifetime. Passive immunity occurs when antibodies are formed by the immune system of another person or animal and transferred to the host. These antibodies act against antigens immediately. This immunity is short-term, lasting only a few weeks or months.
Antigens
Foreign (non-self) substances that initiate immune responses.
Neutrophils
The major WBC’s in the bloodstream and the body’s main defense against pathogenic bacteria. They usually arrive at sites of tissue injury within 90 minutes. They localize the area of injury and phagocytize organisms or particles by releasing digestive enzymes and oxidative metabolites that kill engulfed pathogens or destroy other types of foreign particles. The number increases greatly during the inflammatory process.
Eosinophils
Increase in number and activity during allergic reactions and parasitic infections. In parasitic infections, they bind to and kill the parasites. In hypersensitivity reactions, they produce enzymes that inactivate histamine and leukotrienes and may produce other enzymes that destroy antigen-antibody complexes. Despite these generally beneficial effects, eosinophils also may aggravate tissue damage by releasing cytotoxic substances.
Basophils
Release histamine, a major chemical mediator in inflammatory and immediate hypersensitivity reactions.
Monocytes
Arrive several hours after injury and usually replace neutrophils as the predominant WBC within 48 hours. They are the largest WBCs and their lifespan is much longer than that of the neutrophils. They can phagocytize larger sizes and amounts of foreign material than neutrophils. They can leave blood vessels and enter tissue spaces.
Dendritic cells
Surface macrophages found in peripheral lymphoid and other tissues through which antigens enter the body. Their main function is the presentation of antigen to T lymphocytes, which activates T cells and initiates the adaptive immune response.
Lymphocytes
The main immune cells, and those in tissues are in dynamic equilibrium with those in circulating blood. They continuously travel through blood and lymph vessels from one lymphoid organ to another. Three types are: NK cells, T cells, B cells
NK cells
Destroy infectious microorganisms and malignant cells by releasing powerful chemicals. They are thought to provide the first line of defense against viral infections and other intracellular pathogens while adaptive immune responses are being generated. Also thought to kill certain tumor cells.
T lymphocytes
Main regulators of the immune response. Involved in both cell-mediated and humoral immunity because they direct the activities of B cells and macrophages. They originate in stem cells in the bone marrow and differentiate into immune cells in the thymus gland.
Helper T cells (also called Th or CD4+ cells)
Largest T cell subgroup. Regulate virtually all immune functions by producing cytokines, which stimulate the growth of bone marrow and other cells of the immune system. Also activate macrophages and facilitate phagocytosis.
Cytotoxic T cells (also called TC or CD8+ cells)
Recruited and activated by helper T cells. They bind to antigens on the surfaces of target cells and damage or kill them. They persist in tissues for months and are especially lethal to virus-infected cells because virus particles become entrapped in the membranes of the cells. They can also destroy malignant cells, transplanted organs, and play a role in delayed hypersensitivity reactions.
B lymphocytes
Involved in humoral immunity. They secrete antibodies that can neutralize pathogens before their entry into host cells. B cells must be activated by antigens before they can fulfill their immune functions. They originate from stem cells in the bone marrow. In response to an antigen, B cells multiply rapidly, enlarge, and differentiate into plasma cells, which then produce antibodies to opposite the antigen. Immunoglobulins are secreted into lymph and transported to the bloodstream for circulation throughout the body.
IgG
Most abundant immunoglobulin. Protects against bacteria, toxins, and viruses as it circulates in the bloodstream. Crosses the placenta to provide maternally acquired antibodies (passive immunity) to the infant.
IgA
Main immunoglobulin in mucous membranes and body secretions. Found in saliva, breast milk, and nasal, respiratory, prostatic, and vaginal secretions.
IgM
Protects against bacteria, toxins, and viruses that gain access to the bloodstream. Acts only in the bloodstream.
IgE
Binds to mast cells and basophils. Involves in parasitic infections and hypersensitivity reactions, including anaphylaxis. Sensitizes mast cells, which then release histamine and other chemical mediators that cause bronchoconstriction, edema, urticaria, and other manifestations of allergic reaction.
