Final answer:
Lymphocytes are white blood cells essential to the immune response, including two main types, B cells and T cells. B cells produce antibodies against pathogens, and T cells attack infected cells or manage immune responses. These cells are a critical part of the adaptive immune system, enabling the body to remember and defend against specific pathogens.
Step-by-step explanation:
Lymphocytes Overview
Lymphocytes are a type of white blood cell (WBC) that are central to the body's immune response. Playing a critical role in adaptive immunity, lymphocytes consist of two major types, known as B cells and T cells. These cells are distinguished by their surface markers and the molecules they secrete, with B cells being responsible for producing antibodies that target and neutralize pathogens, and T cells that destroy infected cells or regulate immune response through the release of chemicals.
The human body contains approximately 2 trillion lymphocytes, constituting about one-third of all leukocytes. The majority of lymphocytes reside within the lymphatic system—such as the lymph, lymph nodes, and organs like the spleen and tonsils—with only a small fraction circulating in the bloodstream. Lymphocytes originate from lymphoid stem cells in the bone marrow and continue their development in lymphatic tissues. Morphologically, whether B or T cells, lymphocytes typically exhibit a large central nucleus surrounded by a thin layer of cytoplasm.
In terms of immune function, B cells mature in the bone marrow and are integral to antibody production, while T cells undergo maturation in the thymus and are vital for directly attacking infected cells or aiding in immune regulation. Together, B cells and T cells form the adaptive arm of the immune system, capable of creating lasting memory and immunity to specific pathogens, thus providing protection against recurrent infections.