Overview of Human Immune System and White Blood Cells
Our immune system is responsible for detecting and eliminating pathogens and tumor cells. It makes up our natural disease prevention system, of which white blood cells are a critical component.
White blood cell can be broken down into:
- Lymphocytes (makes up 30% of total white blood cells count, popularly expressed as WBC),
- neutrophils (constitute 60% of WBC, also known as polymorph nuclear leukocytes in the medical field, or simply PMNs, or “polys”), and,
- other blood cell types, which collectively contribute to the balance 10% of WBC. These are bands (2%), basophils (1%), eosinophils (2%) and monocytes (5%).
Production of White Blood Cells
The body parts responsible for manufacturing white blood cells are the:
- lymphoid tissues in the spleen, lymph nodes, and thymus gland – these are the source of lymphocytes, and,
- bone marrow – this is the primary source of neutrophils, bands, basophils, monocytes and eosinophils.
Measurement of WBC
Medical practitioners use WBC measurement to gauge our natural defense ability against infections, ascertain the presence and type of infection within us, track how we respond to treatment administered for infection, check for side effects, and verify if complications were caused by the treatment.
Often, doctors are dependent on both the absolute count and relative count of white blood cells to guide their judgments on their decisions.
As a general guideline, these are some critical values (in term of absolute numbers) concerning WBC:
- WBC measurement should be between 2000 and 30,000
- Lymphocytes should be less than 500
- Neutrophils should be less than 500
Variation on the White Blood Cell Composition
Note that the composition may vary from time to time, and from one person to another. However, the changes within individuals are primarily driven by pre-existing medical conditions. It is usually observed that changes only occur in one cell type. When all cell types are affected, medical experts consider this as hemoconcentration.
For example, in the case of bacterial infection, sufficiently high neutrophil count (which reside within the blood stream) will converge at the infected tissue to tackle the invading bacteria. The high concentration of neutrophils is often the reason behind abscess (symptom characterized by of a localized accumulation of pus right at the center of the inflamed tissue). The amount of neutrophils produced varies in direct proportion to the severity of such bacterial infection. When this happens, it would result in a higher white blood cell count than normal. When readings on WBC are low, it suggests that insufficient neutrophils levels are available to counter the bacterial infections.
The normal range or the relative amount of neutrophils is within 50-60% range while absolute cell count should be 3000-7000.
Sometimes, a smaller reading of WBC is also an indication of low lymphocytes. Lymphocytes are responsible for singling out foreign objects caused by microorganism (such as bacteria or viruses). Antibodies and cells are subsequently produced to deal with them.