Freebase(0.00 / 0 votes)Rate this definition: Arbol is a programming language which has been primarily developed for use in Genetic Programming experiments. It is a functional programming language inspired by the ideas of other small and esoteric languages.
Causes. In most cases of colon or rectal cancers, the cause or causes are unknown. Defects in genes that normally protect against cancer play the major role in causing polyp cells to continuously change and become cancerous.
Infection with viruses or bacteria triggers the immune system to release proteins called antibodies. The specific part of the virus or bacterium that triggers the antibody response is called an antigen. Once produced by the body (specifically, by the lymphoid tissue, which is part of the body's immune system), antibodies circulate in the bloodstream until they come into contact with an antigen.