White blood cells are present in our blood which protect our body from foreign antigens like bacteria, viruses, etc. When these white blood cells decrease abnormally in number then this condition is called leukopenia.
White blood cells contain different cell which protect our body from different type of infections. So there are different types of leukopenia according to the particular white blood cell whose number became low.
For example when neutrophils number in the body decrease it is called neutropenia. So the correct answer is leukopenia.
