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Immune System Vocabulary
Pathogen – “germ”; anything that makes one sick, other than a genetic cause
Immune system – in a vertebrate, the defense against pathogens
Leukocytes – white blood cells
Innate immunity – all animals have this defense against pathogens; includes barriers and inflammation
Adaptive immunity – defense against pathogens which only vertebrastes have. Includes ability to make
antibodies, and recognize antigens for precise killing of infected cells.
Inflammatory response – second line of defense, in which mast cells produce histamines to open
capillaries allowing WBC’s to pass into an affected area and engulf pathogens.
Mast cells – as part of the inflammatory response, these cells produce histamines to allow WBCs to
enter infected areas
Histamines – chemicals that trigger the dilation of capillaries to allow WBCs to enter an infected area
Phagocytes – a class of WBCs that engulf pathogens they recognize as being non-self
Neutrophils –WBCs that make up the highest % of immune system cells in our bodies; these have a short
life span; they patrol the blood stream and lymph to rapidly engulf anything they determine to be nonself
Natural killer cells – WBCs that spray areas of infected cells, indiscriminately killing both infected and
healthy cells.
Macrophages – “big eaters”; these WBCs engulf large invaders, and display their antigen bits on their
cell surface.
Dendritic cells – WBCs that engulf cells and display their antigen bits on their cell surface.
Antigen – anything that elicits a response from the immune system. Generally, this is part of a
pathogen.
Major Histocompatability Complex (I & II)– the combination of a cell’s own protein marker (I), with an
antigen that is displayed on the cell surface (II).
Antigen presenting cell – any cell that has engulfed a pathogen and is displaying part of the pathogen on
its cell surface, in an effort to trigger the adaptive immune response
Interleukin / cytokines – chemical substances released by cells of the immune system to alert other cells
of a need to respond. The response can be any range of things, such as raising body temperature setpoint, to stimulating production of T and B cells.
Lymphocytes – T and B cells
Cell mediated response – part of the adaptive immune response, in which T cells elicit B cells to produce
antibodies, and also go themselves to destroy pathogens
Humoral response – part of the adaptive immune response, in which B cells produce antibodies to
incapacitate pathogens.
T cytotoxic cells – cells that recognize specific antigens and kill cells infected by them
T helper cells – cells that, once triggered by an antigen-presenting cell, induce production of cytotoxic T
cells and find B cells specific to that antigen to start producing antibodies
B Plasma cells – produce antibodies
B memory cells – lymphocytes that display antibodies on their surfaces to be activated by helper T cells
Antibodies – molecules specific to specific antigens; these molecules bind to the antigens to incapacitate
them in one of various ways
Epitope – the part of an antigen that binds to an antibody
Virus – a non-living entity, made up of a protein coat, and containing RNA or DNA; these hijack a cell’s
protein synsthesis mechanism to begin producing copies of themselves.
HIV – the virus that causes AIDS
Primary immune response – the first time the body is exposed to a pathogen; it may take weeks for a
full attack to mount with many cytotoxic T cells and plasma B cells working together to fight the invader
Secondary immune response – a quick reaction to an infection, due to a previous infection by the same
pathogen. Memory T and B cells are rapidly engaged to deploy antibodies and killer T cells to attack
invader.
Vaccine – a preventative measure against viruses; generally these are weaker forms of actual pathogens,
against which the body learns to produce antibodies, so that in the case of a real infection, a secondary
immune response will be engaged
Active immunity – the body produces its own antibodies against a certain pathogen
Passive immunity – the body receives antibodies from another source, such as mother’s milk