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.
Every effective immune response involves T-cell activation; however, T-cells are especially important in cell-mediated immunity, which is the defense against tumor cells and pathogenic organisms inside body cells. They are also involved in rejection reactions.umoral immunity is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B-cell). Secreted antibodies bind to antigens on the surfaces of invading microbes, which flags them for destruction. Humoral immunity refers to antibody production, and all the accessory processes that accompany it.