Lymphocytes are a type of white blood cell (leukocyte) that plays a crucial role in the immune system, which is the body’s defense mechanism against infections and diseases. They are produced in the bone marrow and are found primarily in the lymphatic system, which includes the lymph nodes, spleen, thymus, and lymphoid tissues.
There are three main types of lymphocytes:
- T cells (T lymphocytes): These cells mature in the thymus gland and play a central role in cell-mediated immunity. They are responsible for recognizing and attacking infected cells, cancer cells, and other pathogens directly.
- B cells (B lymphocytes): These cells mature in the bone marrow. B cells are primarily involved in humoral immunity, which involves the production of antibodies to neutralize pathogens such as bacteria and viruses. When activated, B cells can differentiate into plasma cells, which produce antibodies.
- Natural killer (NK) cells: These cells are a subset of lymphocytes that are capable of recognizing and killing infected or abnormal cells, such as cancer cells or cells infected with viruses. Unlike T cells, NK cells do not require prior activation by antigens.
Lymphocytes work together in a coordinated manner to mount immune responses against invading pathogens while also maintaining tolerance to self-antigens to prevent autoimmune reactions. They are essential for adaptive immunity, which involves the body’s ability to remember past infections and respond more effectively upon subsequent encounters with the same pathogens.