Lymphocytes are a type of white blood cell that are responsible for initiating an immune response when a foreign invader enters the body. These cells are primarily in the tonsils, lymph nodes and the spleen, but they also circulate in the blood
The three primary lymphocyte types, including natural killer cells, B cells and T cells. Natural killer cells respond to antigens in a nonspecific way. B cells create antibodies unique to specific antigens. T cells initiate mediated immunity, a type of response where there are no antibodies. There are three different types of T cells and these include helper T cells, cytotoxic T cells and regulatory T cells.