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.
Here are the steps in an immune response: 1  When an antigen is detected by a macrophage (as describe above under phagocytosis), this causes the T-cells to become activated. 2  The T-cells secrete interleukin 2. 3  From here, the immune response follows 2 paths: one path uses cytotoxic T cells and the other uses B cells.