Immune System

Key Terms –

Pathogens: an infectious agent, or more commonly germ, is a biological agent that causes disease to its host.

Macrophage: a type of phagocyte or white blood cell that digests foreign invaders and damaged tissues.

Antigen: any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies).

Helper T cell: are a sub-group of lymphocytes (a type of white blood cell or leukocyte) that play an important role in establishing and maximizing the capabilities of the immune system.

B cell: a lymphocyte derived from bone marrow that provides immunity; it recognizes free antigen molecules in solution and matures into plasma cells that secrete immunoglobulin (antibodies) that inactivate the antigens.

Antibody: any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response.

Killer cell: a white blood cell that attacks and kills “foreign” cells, including tumor cells and cells infected with bacteria or viruses.

Cytotoxic T cell: a type of white blood cell that can directly destroy specific cells.

Memory cell: a subset of T-cells and B-cells that have been exposed to specific antigens and can then proliferate (recognize the antigen and divide) more readily when the immune system re-encounters the same antigens.

Problems of the Immune System –

Severe combined immunodeficiency (SCID): is also known as the "bubble boy disease" after a Texas boy, David Vetter, with SCID who lived in a germ-free plastic bubble. SCID is a serious immune system disorder that occurs because of a lack of both B and T lymphocytes, which makes it almost impossible to fight off pathogens in the body. Its victims are extremely susceptible to infectious diseases and some of them, including David who became known as “the bubble boy”, become famous for living in a completely sterile environment. SCID is the effect of a highly compromised immune system.

HIV (human immunodeficiency virus) infection/AIDS (acquired immunodeficiency syndrome): is a disease that slowly and steadily destroys the immune system. AIDS is caused by HIV, a virus that wipes out a specific lymphocyte, helper T cells. Without these cells, the immune system is unable to defend the body against normally harmless organisms. By damaging your immune system, HIV interferes with your body's ability to fight off life-threatening infections and diseases. Newborns can get HIV infection from their mothers while in the uterus, during the birth process, or during breastfeeding. People can get HIV infection by having unprotected sexual intercourse with an infected person or from sharing contaminated needles for drugs, steroids, or tattoos.