: Certain leucocytes, like neutrophils and macrophages, ingest and destroy harmful germs and cellular debris.

The primary role of leucocytes is to protect the body against infectious diseases and foreign entities. They achieve this through several critical processes:

: The most numerous, acting as first responders to infection.

: Specific cell adhesion molecules (CAMs) allow leucocytes to stick to vascular endothelial cells, a process essential for reaching the site of an injury or infection.

: They move from the bloodstream into tissues via the lymphatic vasculature using chemokine-directed "amoeboid movement".

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

: Primarily involved in battling parasitic infections and allergic responses.

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