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.
Activated B cells and T cells that recognize foreign protein antigen in the peripheral lymphoid tissue come. together to initiate humoral immune response. Within one or two days of antigen administration, naÃ¯ve CD4+. T cells recognize antigen presented by professional APCs in the T cell area of lymphoid organs.