While the tadpoles of competing species may complete metamorphosis in as little as just a few short months, Bullfrog tadpoles can remain in the same state for as long as one to two years before they actually become adult frogs.
Two types of white blood cells called lymphocytes are vital to the specific immune response. Lymphocytes are produced in the bone marrow, and mature into one of several subtypes. The two most common are T cells and B cells. An antigen is a foreign material that triggers a response from T and B cells.
When foreign particles or antigens invade the body, the various types of immune system cells work in combination to recognize and destroy them. The B lymphocytes are triggered in the process producing antibodies, which are specialized proteins that block specific antigens.he immune system is composed of a number of cells, tissues and organs that work in association and attacks the disease causing microorganisms and protect the human body.