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.
1 In the effector phase of the adaptive immune response, secretory antibodies prevent infection at mucosal surfaces of the respiratory tract, while circulating antibodies diffuse to and protect the lungs. 2  Cytotoxic T lymphocytes (CTLs) contribute to elimination of the infection by lysing virus-infected cells.igure 16 Immune responses to viral infections. Innate immune mechanisms include the production of cytokines and the activation of antigen-presenting cells (macrophages and dendritic cells) and natural killer (NK) cells.