Lymphocytes are white blood cells that are part of the body's immune system.
Lymphocytes are types of white blood cells that are part of the body's immune system. The immune system is composed of network of immune cells including lymphocytes that function together to protect the body against foreign substances, such as bacteria or cancer cells that can cause illness and diseases. Lymphocytes are produced in the bone marrow and can be found in the blood and lymph tissue. The two groups of lymphocytes are known as B lymphocytes (B cells) and T lymphocytes (T cells).