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.
1 7 - Once activated, the Helper T cell starts to divide and produce special proteins to signal other immune cells. 2  The activated Helper T cell will in turn activate other T cells to attack the specific antigen 3  (). It also can go on to activate B cells and create an antibody-mediated response. cells are like the police chiefs of white blood cells. T cells are white blood cells called lymphocytes. There are many different types of T cells that all perform different functions, but among the most important are Helper T cells and Killer T cells.