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.
B Cells are activated primarily in response to extracellular pathogens (mostly bacteria). There are 2 main types of T-Cell, each of which is part of Cell-Mediated Immunity. CD8 T-cells, named for its CD8 surface marker, are the âCytotoxicâ T-Cell.