An antigen that stimulates an allergic response.
A Y-shaped protein produced by plasma cells during an adaptive immune response that recognizees and binds to a specific antigen because of the shape of the molecule. They defend against invaders in a variety of ways, including neutralization, agglutination and precipitation, or activation of the complement system.
Immune system responses conducted by B cells that produce antibodies and that defend primarily against enemies that are free in body fluids, including toxins or extracellular pathogens, such as bacteria or free viruses.
Antibody-Mediated Immune Response
A substance that is recognized as foreign by the immune system. Triggers an immune response.
An immune response misdirected against the body's own tissues.
Immune system responses conducted by T cells that protect against cellular threats, including body cells that have become infected with viruses or other pathogens and cancer cells.
Cell-Mediated Immune Response
A type of T lymphocyte that directly attacks infected body cells and tumor cells by relasing chemicals called perforins that cause the target cells to burst.
Cytotoxic T Cells
The kind of T lmphocyte that serves as the main switch for the entire immune response by presenting the antigens to B cells and by secreting chemicals that stimulate other cells of the immune syste. It is also known as a T4 cell or a CD4 cell after the receptors on its surface.
Helper T Cells
A substance released by basophils and mast cells during an inflammatory response that causes blood vessels to widen (dilate) and become more permeable.
The body's response to specific targets not recognized as belonging in the body.
Small nodular organs found along lymph vessles that filter lymph. They contain macrophages and lymphocytes, cells that play an essential role in the body's defense system.
Various organs that belong to the lymphatic system, including the tonsils, spleen, thymus, and Peyer's patches.
A lymphocyte (B cell or T cell) of the immune system that forms in response to an antigen and that circulates for a long period of time; such cells are able to mount a quick immune response to a subsequent exposure the same atigen.
Nonspecific Defense Mechanisms
Temporary immune resistance that developes when a person receives antibodies that were produced by another person or animal.
The immune response that occurs during the body's first encounter with a particular antigen.
Primary Immune Response
Blood cell-forming connective tissue found in the marrow cavity of certain bones.
Red Bone Marrrow
Secondary Immune Response
Specific Defense Mechanisms
A type of T lymphocyte that turns off the immune response when the leval of antigen falls by releasing chemicals that dampen the activity of both B cells and T cells.
Suppressor T Cells
Tonsisls and Adenoids
Minute infectious agents that consists of a nucleic acid encased in protein. It cannot replicate outside a living host cell.