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.
The third line of defence of immune system has strategize to eliminate or control the pathogen either by employing T cells which is called as cell mediated immunity or employing B cells which will produce antibodies to eliminate pathogen and is called as humoral immunity.