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 Immune system is a complex network of cells (such as lymphocytes) and organs that work together to defend the body against foreign substances (antigens) such as bacteria, a virus or tumor cell.When the body discovers such a substance several kinds of cells go into action in what is called an immune response.ymphocytes are divided mainly into B and T cells. 1  B lymphocytes produce antibodies-proteins (gamma globulins) that recognize foreign substances (antigen) and attach themselves to them. 2  B lymphocytes (or B cells) are each programmed to make one specific antibody.