Glossary I-L

Icosahedral: A twenty-sided polyhedron. Many viral capsids take icosohedral forms - the twenty-sided crystalline shape is the most efficient shape that can be built from the smallest number and size of capsomeres, conserving host cell energy for the production of more viruses.

Immunity: The physiologic state which makes the body able to recognize materials as foreign to itself and neutralize, eliminate, or metabolize them with or without injury to its own tissues.

Immune system: A sophisticated screening system which vertebrates possess, which continually checks the bloodstream for the presence of any foreign cells or molecules. When an infection is detected, the invading microbes (viruses, bacteria, fungi, etc.) are attacked and destroyed. Without such a defense system against infection, no vertebrate could survive for a long.

Immune system: The system which secures the body from harm by "fighting" against the harmful effects from pathogenic agents or influences.

Immunoglobulin: A protein molecule functioning as a specific antibody; it brings about the humoral phase of immunity.

Incidence: The frequency at which an event occurs, such as the number of cases of a disease.

Inflammation: A tissue reaction to irritation, infection or injury, marked by localized heat, swelling, redness, pain, and sometimes loss of function.

Influenza A: A contagious infectious disease attributed to a filterable virus and causing fever, headache, pain in the back and limbs, and an inflammation of the respiratory tract.

Insulin: A hormone produced in the islets of Langerhans in the pancreas, concerned with the regulation of carbohydrate metabolism by controlling glucose levels in the blood; it is extracted from the pancreas of beef or pork for use in the treatment of diabetes.

Interferon: A protein substance produced by body cells in response to invasion by viruses and other intracellular parasites; it interferes with the synthesis of new virus and is effective against certain protozoal parasitic infections.

Jaundice: Yellow pigmentation of the skin and/or eyes caused by high levels of bilirubin in the blood. Jaundice is normally the result of liver damage.

Ketone bodies: Acetoacetic acid, acetone, and beta-hydroxybutyrate present in excess in the blood and urine of diabetics.

"Killer T-Cell": T-lymphocytes that have cytotoxic activity against target

cells coated with a specific antibody.

Latency: In order to increase their chances of survival and successful avoidance of the immune system, many viruses lie dormant for a defined period before reproducing within their host cells, or many launch periodic infections and reinfections of a host over a period of years, even a lifetime. This period of dormancy is known as latency.

Lipid: The fats and fat-like materials which, together with carbohydrates and proteins, constitute the main structural substances in the living cell.

Liver: A large, dark-red organ in the human body located in the mid-abdomen region. It is one of the most important organs in the human body, and is intimately involved in almost every part of the body's processes.

Liver failure: A condition in which the liver no longer carries out, or adequately carries out, its functions in the body.

Liver transplant: The transfer of a healthy liver from one individual to another.

Lysosome: Special structures within cells that contain powerful enzymes capable of breaking down organic materials, used for the recycling of materials within the cell, and, in some circumstances, the destruction of a cell.