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 then attacks that cell. Some white blood cells (B cells) recognize invaders, or antigens, directly. When a B cell recognizes and attaches to the antigen, it produces antibodies, which coat the surface of the virus or bacteria to stop it from multiplying or infecting other cells.This process is called neutralization.ther white blood cells (T cells) need help from cells that first ingest the invader and break it into fragments. The fragments are then presented to the T cells so that they can recognize and destroy them. These helper cells are called antigen presenting cells.