Active immunity

Immunity developed from an individual’s own immune system.

Acute inflammation

Inflammation occurring for a limited time period; rapidly developing.

Adaptive immune response

A relatively slow but very specific and effective immune response controlled by lymphocytes.

Afferent lymphatic vessels

Vessels that lead into a lymph node.

Allergens

Antigens that evoke type 1 hypersensitivity (allergy) responses.

Allergist

Specialist who specializes in treating individuals with a hypersensitivity to allergens.

Allergy

Inflammatory response due to a hypersensitivity to a substance that normally is harmless or would not cause an immune response in most people.

Anaphylactic shock

A severe and sometimes life-threatening immune system reaction to an antigen that a person has been previously exposed to. The reaction may include itchy skin, edema, collapsed blood vessels, fainting, difficulty in breathing, and death.

Antibody

A protein made by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response). Each antibody can bind to only one specific antigen. The purpose of this binding is to help destroy the antigen.

Antigens

Substances that provokes an immune response. This happens because the immune system sees the antigen as foreign, or ‘non-self” (does not belong in that body).

Apoptosis

Programmed cell death.

Autoimmune diseases/disorders

Disorders in which the immune system overreacts and begins to attack itself.

B cells

Lymphocytes that act by differentiating into an antibody-secreting plasma cell.

Barrier defenses

Antipathogen defenses deriving from a barrier that physically prevents pathogens from entering the body to establish an infection.

Bone marrow

Tissue found inside bones; the site of all blood cell differentiation and maturation of B lymphocytes.

Bronchus-associated lymphoid tissue (BALT)

Lymphoid nodule associated with the respiratory tract.

CD4 T Cells

CD4 is the receptor that HIV uses to get inside T cells and reproduce. CD4+ helper T cells play an important role in T cell immune responses and antibody responses.

Chemokine

Soluble, long-range, cell-to-cell communication molecule.

Chemotaxis

Movement in response to chemicals; a phenomenon in which injured or infected cells and nearby leukocytes emit the equivalent of a chemical “911” call, attracting more leukocytes to the site.

Chronic inflammation

Ongoing inflammation that can be caused by foreign bodies, persistent pathogens, and autoimmune diseases such as rheumatoid arthritis.

Chyle

Lipid-rich lymph inside the lymphatic capillaries of the small intestine.

Cisterna chyli

A sac-like chamber that receives lymph from the lower abdomen, pelvis, and lower limbs by way of the left and right lumbar trunks and the intestinal trunk.

Complement

Enzymatic cascade of constitutive blood proteins that have antipathogen effects, including the direct killing of bacteria.

Cytokine

A signaling molecule that allows cells to communicate with each other over short distances.

Deep lymphatic vessels

Lymphatic vessels of the organs.

Efferent lymphatic vessels

Vessels that lead out of a lymph node.

Erythroblastosis fetalis

An immune reaction between maternal and fetal blood due to the Rh antigen; also known as hemolytic disease of the newborn (HDN).

Genetic recombination

The combining of gene segments from two different pathogens.

Graft-versus-host disease (GVHD)

A condition that can occur in bone marrow transplant recipients; occurs when the transplanted cells mount an immune response against the recipient’s tissue.

Histamine

A vasodilator involved in the inflammatory response.

Human immunodeficiency virus (HIV)

An infectious disease transmitted through semen, vaginal fluids, and blood that suppresses the immune system. HIV infection may be managed with antiviral drugs or may progress to acquired immune deficiency syndrome (AIDS).

Hypersensitivities

Reacting to something that would not normally evoke a reaction.

Immune system

Series of barriers, cells, and soluble mediators that combine to response to infections of the body with pathogenic organisms.

Immunity

Resistant to the effects of pathogens.

Immunodeficiency

The decreased ability of the body to fight infections and other diseases.

Immunological memory

Ability of the adaptive immune response to mount a stronger and faster immune response upon re-exposure to a pathogen.

Immunology

The study of the body’s immune system.

Induration

A firm, raised reddened patch of skin.

Inflammation

Basic innate immune response characterized by heat, redness, pain, and swelling.

Innate immune response

Fast-acting non-specific immune mechanisms that are present from birth.

Intercellular

Between cells.

Interferons

Early induced proteins made in virally infected cells that cause nearby cells to make antiviral proteins.

Interstitial fluid

Extracellular fluid not contained within blood vessels.

Interstitial space

Spaces between individual cells in the tissues.

Intracellular

Inside the cell membrane or within the cell.

Leukemia

A cancer involving an abundance of leukocytes.

Lymph

The term used to describe interstitial fluid once it has entered the lymphatic system.

Lymph node

One of the bean-shaped organs found associated with the lymphatic vessels.

Lymphatic capillaries

Smallest of the lymphatic vessels and the origin of lymph flow.

Lymphatic system

Network of lymphatic vessels, lymph nodes, and ducts that carries lymph from the tissues and back to the bloodstream.

Lymphatic trunks

Large lymphatics that collect lymph from smaller lymphatic vessels and empties into the blood via lymphatic ducts.

Lymphocytes

The second most common type of leukocyte and are essential for the immune response.

Lymphoid nodules

Unencapsulated patches of lymphoid tissue found throughout the body.

Lymphoma

A form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues. These leukocytes do not function properly, and the patient is vulnerable to infection.

Macrophage

A large cell derived from a monocyte; they participate in innate immune responses.

Major histocompatibility complex (MHC)

Protein structures found on the outside of cells that help the immune system recognize non-self antigens.

Mast cell

Cell found in the skin and the lining of body cells that contains cytoplasmic granules with vasoactive mediators such as histamine.

Memory T cells

Long-lived immune cells reserved for future exposure to a pathogen.

Monocyte

A type of immune cell that is made in the bone marrow.

Mucosa-associated lymphoid tissue (MALT)

Lymphoid nodule associated with the mucosa.

Mucous membranes

Epithelial membranes that line the body cavities and hollow passageways that open to the external environment.

Naïve lymphocyte

Mature B or T cell that has not yet encountered antigen for the first time.

Natural killer cell (NK)

Cytotoxic lymphocyte of innate immune response.

Neutrophil

Phagocytic white blood cell recruited from the bloodstream to the site of infection via the bloodstream.

Opsonization

A process by which an antibody or an antimicrobial protein binds to a pathogen, thereby marking it as a target for phagocytes.

Passive immunity

Transfer of immunity to a pathogen to an individual that lacks immunity to this pathogen usually by the injection of antibodies.

Pathogen

An organism that causes a disease.

Phagocytosis

Movement of material from the outside to the inside of the cells via vesicles made from invaginations of the plasma membrane; process where some white blood cells engulf invading microorganisms.

Plasma cells

A type of B lymphocyte that produces antibodies, which bind to specific foreign or abnormal antigens in order to destroy them.

Primary adaptive response

Immune system’s response to the first exposure to a pathogen.

Primary lymphoid organs

Site where lymphocytes mature and proliferate; for example, red bone marrow and the thymus gland.

Right lymphatic duct

Drains lymph fluid from the upper right side of the body into the right subclavian vein.

Staphylococcus aureus

A bacteria that is commonly found in minor skin infections, as well as in the nose of some healthy people.

Secondary adaptive response

Immune response observed upon re-exposure to a pathogen, which is stronger and faster than a primary response.

Secondary lymphoid organs

Sites where lymphocytes mount adaptive immune responses, examples include lymph nodes and spleen.

Seroconversion

The reciprocal relationship between virus levels in the blood and antibody levels.

Severe combined immunodeficiency disease (SCID)

A rare, inherited disease that is marked by a lack of B and T lymphocytes.

Spleen

Secondary lymphoid organ that filters pathogens from the blood (white pulp) and removes degenerating or damaged blood cells (red pulp).

Superficial lymphatics

Lymphatic vessels of the subcutaneous tissues of the skin.

Systemic lupus erythematosus (SLE)

A chronic, inflammatory, connective tissue disease that can affect the joints and many organs; also called lupus.

T cell

Lymphocyte that acts by secreting molecules that regulate the immune system or by causing the destruction of foreign cells, viruses, and cancer cells.

Thoracic duct

Large duct that drains lymph from the lower limbs, left thorax, left upper limb, and the left side of the head.

Thymocytes

A type of white blood cell that is part of the immune system and develops from stem cells in the bone marrow; also called T cells and T lymphocytes.

Thymus

Primary lymphoid organ, where t lymphocytes proliferate and mature.

Tissue typing

The determination of major histocompatibility complex (MHC) molecules in the tissue to be transplanted to better match the donor to the recipient.

Tonsils

Lymphoid nodules associated with the nasopharynx.

Vaccine

A killed or weakened pathogen or its components that, when administered to a healthy individual, leads to the development of immunological memory (a weakened primary immune response) without causing much in the way of symptoms.

Vasodilation

The physiological widening of blood vessels by relaxing the vascular smooth muscle.

Wheal and flare response

A soft, pale swelling at the site surrounded by a red zone.