A lymphocyte is a type of white blood cell which helps to recognize and fight infection as part of the immune system. Also in the immune system are proteins called antibodies, which attach to harmful substances such as microbes and help destroy them. Lymphocytes can be divided into two main groups, known as T cells and B cells. An important relationship between B lymphocytes and antibodies exists, because B cells are able to develop into what are called plasma cells. Plasma cells are responsible for releasing antibodies into the circulation.
Lymphocytes and antibodies are vital parts of the human immune response. B and T cells work together to recognize and dispose of antigens such as bacteria and viruses. Antibody production is an essential part of the process and, without antibodies, humans would soon die from infections. Inside the immune system, both B and T cells recognize their own specific antigens, which attach to receptors on their cell surfaces. Some T cells then activate B cells, while others kill infected cells.
There are many different B and T lymphocytes and antibodies, able to respond to every antigen which might invade the body. When a B cell has been activated by a T cell, it divides and develops into antibody-secreting plasma cells and memory cells which remember antigens. Initially, the antibodies made by a developing B cell are not released but attach to the cell surface, forming antigen receptors. Then, the B cell matures into a plasma cell that can secrete thousands of antibodies every second. All of the antibodies produced by a plasma cell will bind to the same type of antigen that originally triggered their production.
When antibodies bind to their specific antigens they neutralize them, or make them attractive to other immune cells which consume and destroy them. A further connection between lymphocytes and antibodies is seen when antigens bind to those B cell receptors which were formed from the first antibodies to be produced. This binding helps activate more B cells, stimulating them to develop into antibody-secreting cells and memory cells.
The structures of lymphocytes and antibodies are quite different. In most cases, a lymphocyte such as a B cell or T cell is what is known as an agranular cell, where the gel, or cytoplasm, that fills the cell is clear. The only granular lymphocytes are called natural killer cells, and these differ from B and T cells in that they are not specific and can recognize different kinds of antigens. Antibodies are not cells. They are typically Y-shaped proteins, with antigen-binding sites on the arms of the Y and cell receptor binding sites on its tail.