bio: bacteria, virus, and immune system

capsid

the protein shell that encloses a viral genome

lytic cycle

A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of the host cell

lysogenic cycle

A type of bacteriophage replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome.

pathogen

An agent, such as a virus, bacteria, or fungus, that causes disease

innate immunity

immunity that is present in an animal before exposure to pathogens and is effective from birth. includes barriers, phagocytic cells, antimicrobial proteins, and the inflammatory response and natural killer cells.

phagocytosis

Cellular “eating”; a type of endocytosis in which a cell engulfs macromolecules, other cells, or particles into its cytoplasm

macrophages

A large, amoeboid, phagocytic white blood cell that functions in innate immunity by destroying microbes and in adaptive immunity as an antigen-presenting cell

natural killer cells

Cell type that provides an innate immune response by attacking cancer cells and infected body cells, especially those harboring viruses

interferon

An innate defensive protein produced by virus-infected vertebrate cells and capable of helping other cells resist viruses

complement system

A family of innate defensive blood proteins that cooperate with other components of the vertebrate defense system to protect against microbes; can enhance phagocytosis, cause the rupture of pathogens, and amplify the inflammatory response

inflammatory response

An innate body defense in vertebrates caused by a release of histamine and other chemical alarm signals that trigger increased blood flow, a local increase in white blood cells, and fluid leakage from the blood. The resulting inflammatory response includes redness, heat, and swelling in the affected tissues

adaptive immunity

A vertebrate-specific defense that is activated only after exposure to an antigen and is mediated by lymphocytes. It exhibits specificity, memory, and self-nonself recognition.

antigen

A foreign (non-self) molecule that elicits an adaptive immune response

antibody

A protein dissolved in blood plasma that attaches to a specific kind of antigen and helps counter its effects; secreted by plasma cells

lymphocytes

type of white blood cell that is chiefly responsible for the adaptive immune response and is found mostly in the lymphatic system

B cells

type of lymphocyte that completes in development in the bone marrow and is responsible for the humoral immune response

T cells

type of lymphocyte that matures in the thymus; T cells include both effector cells for the cell-mediated immune response and helper cells required for both the humoral and cell-mediated adaptive responses.

humoral immune response

branch of adaptive immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids

cell-mediated immune response

the branch of adaptive immunity that involves the activation of cytotoxic T cells, which defend against infected cells

antigen receptor

The general term for a surface protein, located on B cells and T cells, that binds to antigens and initiates the adaptive immune response.

clonal selection

process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen

plasma cells

humoral: Secrete antibodies and are short lived

memory cells

A clone of long lived lymphocytes formed during the primary adaptive immune response. Memory cells remain in the lymph nodes until activated by exposure to the same antigen that triggered their formation. when activated, a memory cell forms a large. clone that mounts the secondary immune response.

cytotoxic T cells

type of lymphocyte that attacks body cells infected with pathogens

Helper T cells

type of lymphocyte that, when activated, secretes stimulatory signals that promote the response of B cells (humoral response) and cytotoxic T cells (cell-mediated response) to antigens