- adaptive immunity
- immunity that has memory and occurs after exposure to an antigen either from a pathogen or a vaccination
- affinity
- attraction of molecular complementarity between antigen and antibody molecules
- allergy
- immune reaction that results from immediate hypersensitivities in which an antibody-mediated immune response occurs within minutes of exposure to a harmless antigen
- antibody
- protein that is produced by plasma cells after stimulation by an antigen; also known as an immunoglobulin
- antigen
- foreign or “non-self” protein that triggers the immune response
- antigen-presenting cell (APC)
- immune cell that detects, engulfs, and informs the adaptive immune response about an infection by presenting the processed antigen on the cell surface
- autoantibody
- antibody that incorrectly marks “self” components as foreign and stimulates the immune response
- autoimmune response
- inappropriate immune response to host cells or self-antigens
- autoimmunity
- type of hypersensitivity to self antigens
- avidity
- total binding strength of a multivalent antibody with antigen
- B cell
- lymphocyte that matures in the bone marrow and differentiates into antibody-secreting plasma cells
- basophil
- leukocyte that releases chemicals usually involved in the inflammatory response
- cell-mediated immune response
- adaptive immune response that is carried out by T cells
- clonal selection
- activation of B cells corresponding to one specific BCR variant and the dramatic proliferation of that variant
- complement system
- array of approximately 20 soluble proteins of the innate immune system that enhance phagocytosis, bore holes in pathogens, and recruit lymphocytes; enhances the adaptive response when antibodies are produced
- cross reactivity
- binding of an antibody to an epitope corresponding to an antigen that is different from the one the antibody was raised against
- cytokine
- chemical messenger that regulates cell differentiation, proliferation, gene expression, and cell trafficking to effect immune responses
- cytotoxic T lymphocyte (CTL)
- adaptive immune cell that directly kills infected cells via perforin and granzymes, and releases cytokines to enhance the immune response
- dendritic cell
- immune cell that processes antigen material and presents it on the surface of other cells to induce an immune response
- effector cell
- lymphocyte that has differentiated, such as a B cell, plasma cell, or cytotoxic T lymphocyte
- eosinophil
- leukocyte that responds to parasites and is involved in the allergic response
- epitope
- small component of an antigen that is specifically recognized by antibodies, B cells, and T cells; the antigenic determinant
- granzyme
- protease that enters target cells through perforin and induces apoptosis in the target cells; used by NK cells and killer T cells
- helper T lymphocyte (TH)
- cell of the adaptive immune system that binds APCs via MHC II molecules and stimulates B cells or secretes cytokines to initiate the immune response
- host
- an organism that is invaded by a pathogen or parasite
- humoral immune response
- adaptive immune response that is controlled by activated B cells and antibodies
- hypersensitivities
- spectrum of maladaptive immune responses toward harmless foreign particles or self antigens; occurs after tissue sensitization and includes immediate-type (allergy), delayed-type, and autoimmunity
- immune tolerance
- acquired ability to prevent an unnecessary or harmful immune response to a detected foreign body known not to cause disease or to self-antigens
- immunodeficiency
- failure, insufficiency, or delay at any level of the immune system, which may be acquired or inherited
- inflammation
- localized redness, swelling, heat, and pain that results from the movement of leukocytes and fluid through opened capillaries to a site of infection
- innate immunity
- immunity that occurs naturally because of genetic factors or physiology, and is not induced by infection or vaccination
- interferon
- cytokine that inhibits viral replication and modulates the immune response
- lymph
- watery fluid that bathes tissues and organs with protective white blood cells and does not contain erythrocytes
- lymphocyte
- leukocyte that is histologically identifiable by its large nuclei; it is a small cell with very little cytoplasm
- macrophage
- large phagocytic cell that engulfs foreign particles and pathogens
- major histocompatibility complex (MHC) I/II molecule
- protein found on the surface of all nucleated cells (I) or specifically on antigen-presenting cells (II) that signals to immune cells whether the cell is healthy/normal or is infected/cancerous; it provides the appropriate template into which antigens can be loaded for recognition by lymphocytes
- mast cell
- leukocyte that produces inflammatory molecules, such as histamine, in response to large pathogens and allergens
- memory cell
- antigen-specific B or T lymphocyte that does not differentiate into effector cells during the primary immune response but that can immediately become an effector cell upon reexposure to the same pathogen
- monocyte
- type of white blood cell that circulates in the blood and lymph and differentiates into macrophages after it moves into infected tissue
- mucosa-associated lymphoid tissue (MALT)
- collection of lymphatic tissue that combines with epithelial tissue lining the mucosa throughout the body
- natural killer (NK) cell
- lymphocyte that can kill cells infected with viruses or tumor cells
- neutrophil
- phagocytic leukocyte that engulfs and digests pathogens
- opsonization
- process that enhances phagocytosis using proteins to indicate the presence of a pathogen to phagocytic cells
- passive immunity
- transfer of antibodies from one individual to another to provide temporary protection against pathogens
- pathogen
- an agent, usually a microorganism, that causes disease in the organisms that it invades
- pathogen-associated molecular pattern (PAMP)
- carbohydrate, polypeptide, and nucleic acid “signature” that is expressed by viruses, bacteria, and parasites but differs from molecules on host cells
- pattern recognition receptor (PRR)
- molecule on macrophages and dendritic cells that binds molecular signatures of pathogens and promotes pathogen engulfment and destruction
- perforin
- destructive protein that creates a pore in the target cell; used by NK cells and killer T cells
- plasma cell
- immune cell that secrets antibodies; these cells arise from B cells that were stimulated by antigens
- regulatory T (Treg) cell
- specialized lymphocyte that suppresses local inflammation and inhibits the secretion of cytokines, antibodies, and other stimulatory immune factors; involved in immune tolerance
- T cell
- lymphocyte that matures in the thymus gland; one of the main cells involved in the adaptive immune system