Lymphocytes are cells that are produced in the lymphoid cells of the bone marrow and that, after production, migrate to the lymphoid organs such as the thymus, spleen or lymph nodes. For this reason they are called lymphatic cells and represent 99% of these cells.
Lymphocytes are the group of cells within the smaller white blood cells and account for about 30% of the total blood. Lymphocytes are part of the leukocytes or white blood cells and are part of an individual's immune system.
There are three types of lymphocytes, which are natural killer cells or NK cells, T lymphocytes and B lymphocytes, and can be identified by their large nucleus. T lymphocytes (mainly generated in the Thymus lymphocyte organ) and B lymphocytes from the bone marrow represent the main components in the adaptive immune response. T lymphocytes are responsible for immune responses at the cellular level, on the other hand, B lymphocytes are responsible for humoral immunity. The function of these lymphocytes is to recognize the invading agents in non-own organisms or antigens, in a process known as the presentation of antigens. At the time these cells recognize a foreign agent in the body they activate the immune response to remove the pathogen or cells infected by the pathogen, where the B lymphocytes respond to this action generating large amounts of antibodies to neutralize the invading agent as bacteria and viruses. T cells divide their attack action, T cells called helper T lymphocytes produce cytokines that direct the immune response, and another group of T cells called cytotoxic T lymphocytes produce toxic granules with which they store enzymes to cause the cells of organisms to die infected by the pathogen. Once the attack is eradicated, B lymphocytes and T lymphocytes are able to produce replicates of the pathogen that they have deleted as memory cells, in order to prepare a rapid and effective attack if the foreign agent is detected again. After activation, B cells and T cells leave a lasting legacy of the antigens that have been found, in the form of memory cells. Throughout the lifetime of an animal these memory cells "remember" each specific pathogen found, and are able to mount a strong and rapid response if the pathogen is detected again.