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Lymphocytes - Definition


Lymphocytes are a type of white blood cell that plays a major role in the immune defense of the body against aggression by external microbial agents. They are produced in the bone marrow and circulate in the blood and lymph vessels. There are several types of lymphocytes, including two main ones. Roughly, T lymphocytes (for "thymus" as they complete their maturation in the thymus) are responsible for cellular immunity destroying cells that have been recognized as infected. B lymphocytes meanwhile produce immunoglobulins, proteins whose role is to destroy antibody molecules recognized as foreign by the body: this recognition is permitted by the recognition of a fragment called an antigen by other white blood cells that will trigger the immune response specific to the antigen, called humoral immunity.