Why white blood cell irregular in shape?

White blood cells change their shape to reach a site of infection.

Explanation:

White blood cells (leukocytes) are part of the immune system and have are responsible for tracking and killing pathogens such as bacteria. An important way white blood cells eliminate pathogens is by 'eating' them (pahgocytosis).

White blood cells circulate in the blood stream, but are usually required at the site of infection inside tissues. For this to happen, the white blood cells have to migrate through the walls of small blood vessels and have to be able to find their way in tissues. This can only occur because the white blood cells are able to change shape.