The Second part is called the Delayed Immune System and is more talked about and less understood than the first. It is much more complicated. Its soldiers are a different type of white blood cell, called the lymphocyte. Initially, the lymphocyte is produced in the bone marrow but lives most of its life in the lymph nodes or in the blood. The lymph nodes are small way stations, where lymphocytes are multiplied and programmed, in preparation for war against invading organisms and tumors.
Lymphocytes circulate in the blood and make up twenty per cent of the white cells.
These two populations of cells network in a complicated way to make the immune system function. Differentiated B-lymphocytes are called Plasma Cells. The number of B-Cells in circulation in the blood results from this dynamic relationship. The antibodies paralyze invading organisms by sticking to their antigens and making them susceptible to be engulfed by yet another group of white cells, called phagocytes or scavenger cells. Some of these scavenger cells engulf the invading organisms, whether they are tumor cells, viruses or bacteria, break them down and process their antigens.