- acellular
- lacking cells
- active immunity
- an immunity that occurs as a result of the activity of the body’s own cells rather than from antibodies acquired from an external source
- adaptive immunity
- a specific immune response that occurs after exposure to an antigen either from a pathogen or a vaccination
- allergy
- an immune reaction that results from immediate hypersensitivities in which an antibody-mediated immune response occurs within minutes of exposure to a harmless antigen
- antibody
- a protein that is produced by plasma cells after stimulation by an antigen; also known as an immunoglobulin
- antigen
- a macromolecule that reacts with cells of the immune system and which may or may not have a stimulatory effect
- antigen-presenting cell (APC)
- an immune cell that detects, engulfs, and informs the adaptive immune response about an infection by presenting the processed antigen on its cell surface
- apoptosis
- the cell death caused by induction of a cell’s own internal mechanisms either as a natural step in the development of a multicellular organism or by other environmental factors such as signals from cells of the immune system
- attenuation
- the weakening of a virus during vaccine development
- autoantibody
- an antibody that incorrectly marks “self” components as foreign and stimulates the immune response
- autoimmunity
- a type of hypersensitivity to self-antigens
- B cell
- a lymphocyte that matures in the bone marrow
- capsid
- the protein coating of the viral core
- cell-mediated immune response
- an adaptive immune response that is controlled by T cells
- complement system
- an array of approximately 20 soluble proteins of the innate immune system that enhance phagocytosis, bore holes in pathogens, and recruit lymphocytes
- cytokine
- a chemical messenger that regulates cell differentiation, proliferation, and gene expression to effect immune responses
- cytopathic
- causing cell damage
- cytotoxic T lymphocyte (TC)
- an adaptive immune cell that directly kills infected cells via enzymes, and that releases cytokines to enhance the immune response
- dendritic cell
- an immune cell that processes antigen material and presents it on the surface of its cell in MHC class II molecules and induces an immune response in other cells
- effector cell
- a lymphocyte that has differentiated, such as a B cell, plasma cell, or cytotoxic T cell
- glycoprotein
- a protein molecule with attached carbohydrate molecules
- helper T lymphocyte (TH)
- a cell of the adaptive immune system that binds APCs via MHC class II molecules and stimulates B cells or secretes cytokines to initiate the immune response
- humoral immune response
- the adaptive immune response that is controlled by activated B cells and antibodies
- hypersensitivity
- a spectrum of inappropriate immune responses toward harmless foreign particles or self-antigens; occurs after tissue sensitization and includes immediate-type (allergy), delayed-type, and autoimmunity
- immune tolerance
- an acquired ability to prevent an unnecessary or harmful immune response to a detected foreign body known not to cause disease
- immunodeficiency
- a failure, insufficiency, or delay at any level of the immune system, which may be acquired or inherited
- inflammation
- the localized redness, swelling, heat, and pain that results from the movement of leukocytes through opened capillaries to a site of infection
- innate immunity
- an immunity that occurs naturally because of genetic factors or physiology, and is not caused by infection or vaccination
- interferon
- a cytokine that inhibits viral replication
- lymph
- the watery fluid present in the lymphatic circulatory system that bathes tissues and organs with protective white blood cells and does not contain erythrocytes
- lymphocyte
- a type of white blood cell that includes natural killer cells of the innate immune system and B and T cells of the adaptive immune system
- macrophage
- a large phagocytic cell that engulfs foreign particles and pathogens
- major histocompatibility complex (MHC) I
- a group of proteins found on the surface of all nucleated cells that signals to immune cells whether the cell is normal or is infected or cancerous; it also provides the appropriate sites into which antigens can be loaded for recognition by lymphocytes
- major histocompatibility complex (MHC) II molecule
- a protein found on the surface of antigen-presenting cells that signals to immune cells whether the cell is normal or is infected or cancerous; it provides the appropriate template into which antigens can be loaded for recognition by lymphocytes
- mast cell
- a leukocyte that produces inflammatory molecules, such as histamine, in response to large pathogens
- memory cell
- an antigen-specific B or T lymphocyte that does not differentiate into an effector cell during the primary immune response but that can immediately become an effector cell on reexposure to the same pathogen
- monocyte
- a type of white blood cell that circulates in the blood and lymph and differentiates into a macrophage after it moves into infected tissue
- natural killer (NK) cell
- a lymphocyte that can kill cells infected with viruses or tumor cells
- neutrophil
- a phagocytic leukocyte that engulfs and digests pathogens
- passive immunity
- an immunity that does not result from the activity of the body’s own immune cells but by transfer of antibodies from one individual to another
- primary immune response
- the response of the adaptive immune system to the first exposure to an antigen
- secondary immune response
- the response of the adaptive immune system to a second or later exposure to an antigen mediated by memory cells
- T cell
- a lymphocyte that matures in the thymus gland
- vaccine
- a weakened solution of virus components, viruses, or other agents that produce an immune response
- viral envelope
- a lipid bilayer that envelops some viruses
- virion
- an individual virus particle outside a host cell
- white blood cell
- a nucleated cell found in the blood that is a part of the immune system; also called leukocytes