: The most numerous, acting as first responders to infection.
: Key players in the adaptive immune system, further divided into T cells (cell-mediated immunity) and B cells (antibody production). Function and Mechanism leucocyte
Leucocytes are generally classified by their cell lineage into or lymphoid cells and further divided based on the presence of granules in their cytoplasm: Granulocytes : Contain visible granules and include: : The most numerous, acting as first responders to infection
: Certain leucocytes, like neutrophils and macrophages, ingest and destroy harmful germs and cellular debris. : The most numerous
: Release histamine and other chemicals during inflammatory reactions. Agranulocytes : Lack visible granules and include:
: They move from the bloodstream into tissues via the lymphatic vasculature using chemokine-directed "amoeboid movement".