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.
A answered. Lymphocytes are different from other types of white blood cells because they recognize and remember invading bacteria and viruses. T lymphocytes, or T cells, are responsible for cell-mediated immunity. T cells come in many types with specific functions, including: Helper T cells direct the immune system. In a rather lengthy process, helper T cells release cytokines. Cytokines stimulate B cells to form plasma cells. Plasma cells form antibodies, which stimulate the production of two other types of T cells: cytotoxic T cells and suppressor T cells. Helper T cells are the cells attacked by the AIDS virus. You can imagine the devastating effect of destroying the T cells that direct the immune system. Cytotoxic T cells release certain chemicals that break open to kill invading organisms.