Leukocytes are a type of blood cell that plays an important role in the immune system, fighting viruses, bacteria and diseases. The number of white blood cells affects the body's immunity in fighting infection (Alham & Herumurti, 2019). When there is an infection caused by bacteria or viruses, the number of leukocytes will increase.

White blood cells have different shapes and characteristics that can be known by examining peripheral blood smears (Siswanto et al., 2020). Types of leukocytes that may be detected in the system are polymorphonuclear neutrophils (PMN), band neutrophils, eosinophils, monocytes and lymphocytes. Leukocyte cells have features or characteristics described by the following figure :