: Key players in the adaptive immune system, further divided into T cells (cell-mediated immunity) and B cells (antibody production). Function and Mechanism

: Release histamine and other chemicals during inflammatory reactions. Agranulocytes : Lack visible granules and include:

: Large cells that migrate into tissues to become macrophages, which engulf debris and pathogens.

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.