K

KAPOSI's SARCOMA (KS):
An AIDS-defining illness consisting of individual cancerous lesions caused by an overgrowth of blood vessels. KS typically appears as pink or purple painless spots or nodules on the surface of the skin or oral cavity. KS also can occur internally, especially in the intestines, lymph nodes, and lungs, and in this case is life threatening. The cancer may spread and also attack the eyes. There has been considerable speculation that KS is not a spontaneous cancer but is sparked by a virus. A species of herpes virus -- also referred to as Kaposi's Sarcoma herpes virus (KSHV) or HHV-8 -- similar to the Epstein-Barr virus is currently under extensive investigation. Up to now, KS has been treated with alpha interferon, radiation therapy (outside the oral cavity), and various systemic and intralesional cancer chemotherapies.

KARNOFSKY SCORE:
A score between 0 and 100 assigned by a clinician based on observations of a patient's ability to perform common tasks. Thus, 100 signifies normal physical abilities with no evidence of disease. Decreasing numbers indicate a reduced ability to perform activities of daily living.

KILLER T CELLS:
Because viruses lurk inside host (e.g., human) cells where antibodies cannot reach them, the only way they can be eliminated is by killing the infected host cell. To do this, the immune system uses a kind of white blood cell, called killer T cells. These cells act only when they encounter another cell that carries a "marker" (i.e., a protein) that links it to a foreign protein -- that of the invading virus. Killer T cells can themselves become infected by HIV or other viruses, or transformed by cancer. Also known as cytotoxic T cells (or cytotoxic T lymphocytes). See NK (natural killer) Cells; Null Cell; T Cells.

KSHV:
Kaposi's Sarcoma Herpes Virus. See Kaposi's Sarcoma.

KUPFFER CELLS:
Specialized macrophages in the liver. See Macrophage.