leucociti

Leucociti, also known as white blood cells (WBCs), are components of the blood that play a central role in the immune system. They protect the body against infections and foreign substances. They originate in the bone marrow and circulate in the bloodstream and lymphatic system, migrating to tissues as needed.

They are broadly classified into granulocytes and agranulocytes. Granulocytes include neutrophils, eosinophils, and basophils; agranulocytes include lymphocytes (T cells, B cells, NK cells) and monocytes. Neutrophils are the most abundant, acting as fast responders by phagocytosing bacteria. Lymphocytes coordinate adaptive immunity; monocytes differentiate into macrophages and dendritic cells; eosinophils defend against parasites and contribute to allergic responses; basophils release histamine and other mediators.

Development and lifespan: Leucociti are produced in the bone marrow from hematopoietic stem cells. They enter the bloodstream and can move into tissues (diapedesis). Lifespans vary; neutrophils circulate for about 6–8 hours in blood and a few days in tissues, whereas lymphocytes can persist for months to years.

Clinical notes: Normal range of total leukocyte count is roughly 4,000 to 11,000 cells per microliter of blood, though reference ranges vary. The differential count expresses percentages of each type. Abnormal WBC counts include leukocytosis (high) and leukopenia (low) and can be caused by infection, inflammation, immune disorders, medications, or bone marrow disorders.

Testing and interpretation: A complete blood count with differential (CBC or CBC with diff) is commonly used to assess leucocytes. Further testing, such as flow cytometry or bone marrow examination, may be used to diagnose specific conditions.