What is white blood cell?
Those blood cells which are colorless, nucleated, capable of active amoeboid movement and concerned with defence mechanism of the body are called white blood corpuscles or leucocytes or simply white blood cells.
What is the meaning of normal white blood cell count?
White blood cells have been classified on the basis of their nuclear structure and staining property of the cytoplasm. They are of mainly two types, those are
Granulocytes are named so, because they have a granular cytoplasm. Granulocytes are ageing divisible into three sub-classes, those are neutrophil, eosinophil and basophil, depending on the staining affinities of their cytoplasmic granules. Those three types of sub classes stay in the normal blood in different numbers and they vary differently in the diseased blood. So to take normal white blood cell count should consider of those three types of granulocytes.
On the other hand the agranulocytes are the leucocytes whose cytoplasm does not contain any granule. Unlike the granulocytes, the nucleus of agranulocytes is not lobed. There are two types of agranulocytes and those are lymphocyte and monocyte. Their count also varies in human blood in normal and abnormal position. This count is also essential for diagnosis of disease.
So, there have five types of white blood cells in human blood. Those are neutrophil, eosinophil, basophil, lymphocyte and monocyte. They present in different numbers in the human blood. Normal white blood cell count may be defined as three types of counts, such as total count, different count and Arneth count.
Number of WBC or normal white blood cell count:
In normal adult human blood, the total count (T.C.) of leucocytes that is, the total number of all varieties of leucocytes per cubic millimetre or microlitre of blood is 6000 to 8000. Counts within 4000 to 11,000 are considered as normal total count of white blood cell. When the total count reduced below of 4000 is called leucopenia and when it increases above 11,000 is called leucocytosis.
The percentage of different varieties of leucocytes that is, the numbered of each variety of white blood cells part hundred leucocytes is known as the tea plant shall count (D.C.). In normal case of adult human blood the differential count is as follows:
Neutrophil --------- 60 to 70%
Eosinophil ---------- 2 to 4%
Basophil ------------ 0 to 1%
Lymphocyte ------ 25 to 30%
Monocyte -------- 5 to 10%
So, we have seen that among the leucocytes, neutrophil are found most in large quantities and basophil found scarcely in normal human blood.
There has another type of normal white blood cell count which is called Arneth count. The percentage of different varieties of neutrophils depending upon the number of nuclear lobes, that is, the number of each varieties of the park hundred neutrophils is called Arneth count or sometimes it is called Arneth index. The Arneth count for normal blood is as follows:
One lobed ------- 5 to 10%
two lobed ------- 25 to 30%
three lobed ----- 45 to 47%
four lobed ------ 16 to 18%
five or more lobed ---- 2%.
Thus we can say the three lobed neutrophils are most abundant (in large number) in the normal white blood cell count. All of the above counts are used in diagnostic measure.