Lymphocytes are produced by precursor cells in the bone marrow. They are found traveling in the blood stream, at sites of infection in large numbers, and in the lymph nodes which are located in the groin area, armpit area, and tonsils. There are also lymphocytes in the appendix and spleen.
One important type of white blood cell is a lymphocyte. These are made in the marrow of your bones. You may have as many as 2 trillion lymphocytes in your bloodstream at any one time. Two major types of lymphocytes involved in protecting the body against invaders are T lymphocyte cells and B lymphocyte cells. T lymphocyte cells destroy cells that have been infected or damaged by the antigens. B lymphocytes are found in immunity-related organs such as the lymph nodes. They direct the making of immunoglobulin E, called IgE. IgE is a special disease-fighting protein known as an antibody. It binds to an antigen in your body, such as bacteria, rendering it harmless. (http://health.discovery.com/centers/articles/articles.html?chrome=c16&article=LC_07¢er=p01)