In our body 500 to 7000 WBC's in per cubic millimetres of blood.in size they are larger than RBC's but less in numbers.
There are two types of RBC
1. lymphocytes made in the lymph node and responsible for antibody production to fight against disease causing microbes.
2. Neutrophils made in the Red bone marrow that are able to engulf microbes and cell debris.
These cells always protect us from microbes and thus we don't fell ill always when microbes enters our body.