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Acquired Immune Deficiency Syndrome (AIDS)

A disorder in which the immune system is gradually weakened and eventually disabled by the human immunodeficiency virus (HIV). HIV destroys T-cells. T-cells are white blood cells that signal other cells to begin an immune response

Active Immunity

Immunity provided by an encounter with an antigen; provides immunologic memory

Antibody-Mediated Immunity

The production of antibodies by B cells in response to an antigen

Antigen (Ag)

Any substance-including toxins, foreign proteins, or bacteria-that, when introduced to the body, is recognized as foreign and activates the immune system

Antigen-Binding Site

The site on an immunoglobulin or T-cell receptor molecule that binds specific antigen

Antigen Presentation

The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell

Antigen-Presenting Cells (APCs)

Cells that capture and present peptides to T lymphocytes


Tissue transplanted from one site to another on the same person

Autoimmune Disease

A disorder in which the immune system attacks the body's own Molecules

B Cells/B Lymphocytes

Lymphocytes that oversee humoral immunity; their descendants differentiate into antibody-producing plasma cells

Cell-Mediated Immunity

Form of acquired immunity; results from activation of T lymphocytes that were previously sensitized to a specific antigen


Chemical attraction causing neutrophil to infected area of tissue


Descendants of a single cell


A group of plasma proteins that normally circulate in inactive forms; when activated by complement fixation, causes lysis of foreign cells and enhances phagocytosis and inflammation

Constant (C) Region

Is nearly the same in all antibodies of the same class and is responsible for the type of antigen-antibody reaction that occurs


The outer surface layer of an organ


Division of the cytoplasm during cell division

Cytoxic (Killer) T Cells

Effector T cell that directly kills foreign cells

Diabetes Mellitus

A disease caused by deficient insulin release or inadequate responsiveness to insulin, leading to instability of the body cells to use carbohydrates at a normal rate


The passage of blood cells through intact vessel walls into the tissues


An abnormal accumulation of fluid in body parts or tissues; causes swelling

Efferent Lymphatic Vessels

Vessel in which lymph and lymphocytes leave a lymph node en route to the blood


A rise of body temperature above the normal. It is caused by cytokines produced in response to infection


Colloid-containing structure in the thyroid gland

Germinal Centers

Area of the lymph nodes within secondary follicles and an area where B cells proliferate, undergo somatic hypermutation and die, causing the node to swell during infection

Hapten (Incomplete Antigen)

Small particle that triggers an immune response only when combining with one of our own proteins

Helper T Cells

The type of T lymphocyte that orchestrates cellular immunity by direct contact with other immune cells and by releasing chemicals called lymphokines; also helps to mediate the humoral response by interacting with B cells.

Adaptive (Specific) Defense System

Protect against specific pathogens, involves lymphocytes

Afferent Lymphatic Vessels

Vessels that bring lymph draining from connective tissue into a lymph node en route to the blood


Clumping of (Foreign) cells, induced by cross-linking of antigen-anti-body complexes


A depressed area where vessels enter and leave an organ


A substance that causes vasodilation and increased vascular permeability

Humoral Immunity

Specific immunity produced by B cells that produce antibodies that circulate in body fluids

Immune Response

Antigen-specific defenses mounted by activated lymphocytes (T cells and B cells)

Immune System

A system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response


The ability of the body to resist many agents (Both living and nonliving) that can cause disease; resistance to disease


The ability of the body's immune cells to recognize (By binding) specific antigens; reflects the presence of plasma membrane-bound receptors


Any congenital or acquired condition that causes immune cells, phagocytes or compliment, to behave abnormally

Immunoglobulins (Igs)

A protein molecule, released by plasma cells, that mediates humoral immunity; an antibody

Immunological Memory

The capacity of the immune system to make quicker and stronger adaptive immune responses to successive encounters with an antigen. Immunological memory is specific for a particular antigen and is long-lived

Inflammatory Response

A line of defense triggered by penetration of the skin or mucous membranes, in which small blood vessels in the vicinity of an injury dilate and become leakier, enhancing the inflitration of leukocytes; may also be widespread in the body

Innate (Nonspecific) Defense System

Consisting of first line of defense (barriers and membranes)


A protein released by infected cells, usually in response to the entry of a virus, that has the property of inhibiting virus replication by attaching to uninfected cells which stimulates the uninfected cell to synthesize another antiviral protein that inhibits viral replication


Grafts between identical twins


Group of polypeptides that dilate arterioles, increase vascular permeability, and induce pain


The watery fluid in the lymph vessels collected from the tissue spaces

Lymph Capillaries

Small, thin walled tubes that collect lymph from interstitial fluid are called

Lymph Nodes

A mass of lymphatic tissue

Lymphatic Collecting Vessels

These receive lymph from lymphatic capillaries, contain more valves than veins, superficial and deep, pass through lymph nodes where it is monitored and cleared of pathogens and cancer cells

Lymphatic System

A system of lymphatic vessels, lymph nodes, and other lymphoid organs and tissues

Lymphatic Vessels

Located deeper within the tissues that has lymph flowing to them from the lymphatic capillaries


A network of lymphatic vessels


Agranular white blood cells formed in the bone marrow that mature in the lymphoid tissue

Lymphoid Organs

Lymph nodes, spleen, and thymus gland


An enzyme found in sweat, saliva, and tears that is capable of destroying certain kinds of bacteria


A phagocytic cell particularly abundant in lymphatic and connective tissues; important as an antigen-presenter to T cells and B cells in the immune response


The central portion of certain organs

Membrane Attack Complexes (MAC)

The complex of terminal complement components that forms a pore in the membrane of the target cell, damaging the membrane and leading to cell lysis

Allergies (Hypersensitivities)

Overzealous immune response to an otherwise harmless antigen


Tissue taken from an unrelated person


A specialized substance produced by the body that can provide immunity against a specific antigen

Memory Cells

Member of T cell and B cell clones that provides for immunologic memory

Monoclonal Antibodies

Pure preparations of identical antibodies that exhibit speficity for a single antigen

Mucosa-Associated Lymph Tissue (MALT)

Small masses of lymph tissue located in: Respiratory tract, digestive tract

Natural Killer (NK) Cells

A specialized lymphocyte with some characteristics of a T cell. Recognize non-antigenic chemical changes on virally infected cells and can attack them directly


Blockage of the harmful effects of bacterial exotoxins or viruses by the binding of antibodies to their functional sites

Passive Immunity

Short-lived immunity resulting from the introduction of "borrowed antibodies" obtained from an immune animal or human donor; immunological memory is not established


Disease-causing microorganism Ex. bacteria, viruses, fungi, etc.

Peyer's Patches

Found in the wall of the small intestine - Resemble tonsils in structure - Capture and destroy bacteria in the intestine


A cell capable of engulfing and digesting particles or cells harmful to the body

Plasma Cells

Member of a B cell clone; specialized to produce and release antibodies

Positive Chemotaxis

Movement toward a chemical stimulus


Formation of insoluble complexes that settle out of solution

Primary Humoral Resonse



An agent or chemical substance that induces fever

Regulatory T Cells

- Release chemicals to suppress the activity of T and B cells - Stop the immune response to prevent uncontrolled activity

Right Lymphatic Duct

Receives lymph from the right arm and right side of the head and thorax

Secondary Humoral Responses

Memory cells once again encounter same bacteria, antibody level peaks 2 to 3 days after response

Self Tolerance

Tolerance by the body's immune system to its own cells and tissues


A term used to describe all the normal constituents of the body to which the immune system would respond were it not for the mechanisms of tolerance that destroy or inactivate self-reactive B and T cells


A dilated channel for passage of blood or lymph


An organ that is part of the lymphatic system; it produces lymphocytes, filters the blood, stores blood cells, and destroys old blood cells.

T Cells/T Lymphocytes

Lymphocytes the mediate cellular immunity; include helper, killer, supressor, and memory cells

Thoracic Duct

Large LEFT lymph vessel in the chest that receives lymph from below the diaphragm and from the left side of the body above the diaphragm


An endocrine gland active in the immune response


A ring of lymphoid tissue around the entrance to the pharynx. In an ideal position (1) to destroy bacteria (which are present in large numbers in the intestine), thereby preventing these pathogens from breaching the intestinal wall, and (2) to generate many "memory" lymphocytes for long-term immunity


Artificial way of tricking the immune system into making anitbodies

Variable (V) Region

Amino-terminal portion of immunoglobulin and T-cell receptor chains that are highly variable and responsible for the antigenic specificity of these molecules


Tissue taken from a different animal species

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