Limfocite

Limfocite, known in English as lymphocytes, are a type of white blood cell central to the adaptive immune system. They are small to medium in size with a large, round nucleus and scant cytoplasm.

Lymphocytes originate from hematopoietic stem cells in the bone marrow. B lymphocytes (B cells) complete maturation in bone marrow, while most T lymphocytes (T cells) mature in the thymus. Natural killer (NK) cells also derive from lymphoid progenitors and mature in various tissues; NK cells are part of the innate immune system but share lymphoid lineage.

Major subsets include B cells, T cells (helper CD4+, cytotoxic CD8+, regulatory), and natural killer cells. B cells produce antibodies, whereas T cells coordinate responses or kill infected cells. NK cells provide rapid cytotoxicity against virally infected or transformed cells, without prior antigen exposure.

Functionally, lymphocytes mediate humoral and cellular immunity and form immunological memory after infection or vaccination.

Clinical notes: Lymphocyte counts can be high (lymphocytosis) or low (lymphocytopenia) in various diseases. Abnormalities are evaluated in infections, immunodeficiencies, or hematologic cancers, and lymphocyte function is a focus of vaccination research and autoimmune disease studies.