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.
B-cells and T-cells When the body needs a more sophisticated immune attack, it turns to its T-cells and B-cells. These cells are the special ops of the immune systemâa line of defense that uses past behaviors and interactions to learn to recognize specific foreign threats and attack them when they reappear.