As part of the immune system, a primary function of lymphocytes is to respond immediately to the presence of foreign matter, viral attacks and invading pathogens. Lymphocytes, which are a type of white blood cell, are found in the blood and certain lymphoid organs.
Lymphocytes make up between 20 to 40 percent of the white blood cells found in adults. There are different types of lymphocytes like B cells, T cells and natural killer cells. The thymus gland is the site where T cells develop. T cells contain T cell receptors that can recognize and attach themselves to various types of antigens.
B cells mature in the bone marrow and these cells also contain receptors that recognize other types of antigens and can bind to them. Natural killer cells are capable of destroying infected cells or certain tumor cells.