Lenfosit

Lenfosit, or lymphocyte in Turkish, is a type of white blood cell that is central to the body's adaptive immune system. They originate from hematopoietic stem cells in the bone marrow and are further developed in primary lymphoid organs. T lymphocytes mature in the thymus, B lymphocytes mature in the bone marrow, and natural killer (NK) cells arise from common lymphoid progenitors with distinct development pathways.

Lymphocytes can be broadly categorized into T cells, B cells, and NK cells. T cells coordinate immune responses and can kill infected or abnormal cells; B cells produce antibodies; NK cells provide rapid responses to virally infected and transformed cells. Lymphocytes circulate between blood, lymph, and secondary lymphoid tissues, where they recognize antigens and mount targeted responses. B cells differentiate into plasma cells that secrete antibodies; helper T cells assist other immune cells; cytotoxic T cells destroy infected cells.

In adults, lymphocytes typically account for about 20–40% of white blood cells, with an absolute count roughly 1.0–4.8 x 10^9/L. Values vary with age and laboratory methods. Lymphocytosis is an elevated lymphocyte count, often seen in viral infections or certain leukemias. Lymphocytopenia is a decreased count and can occur with severe illness, corticosteroid use, or HIV/AIDS.

Clinical relevance includes the use of lymphocyte counts and subsets (such as CD4+, CD8+ T cells; CD19+ B cells; NK cells) in diagnosing infections, immune deficiencies, and hematologic disorders. Abnormal lymphocyte levels can indicate infections, immune dysfunction, or hematologic malignancies.