white blood cells (WBC or leukocytes)

White blood cells

White blood cells also called leukocytes and abbreviated as WBCs are the cells of the human immune system which function has to protect the body from infectious diseases and foreign pathogens.

All White blood cells are produced in the bone marrow from hematopoietic stem cells. These cells have nuclei that differentiate them from the Red blood cells and platelets.

White blood cells can be classified in two ways
1.  By structure
2.  By cell lineage

On the basis of structure, WBCs are classified into two groups which are granulocyte and agranulocytes.

On the basis of cell lineage, they are also classified into two groups which are myeloid cells or lymphoid cells.

Classification on the basis of the structure is the broadest classification which is further divided into 5 main types. These types are,

1.  Neutrophils
2.  Eosinophils
3.  Basophils
4.  Lymphocytes
5.  Monocytes

Per microliter of blood contains 4000 to 11000 white blood cells.

An increase in the number of white blood cells is called leukocytosis.

The decrease in the number of WBCs is known as leukopenia.

Types of white blood cells

The function of white blood cells is to fight against diseases. There are many types of leukocytes which perform their specific function. And due to it, they are classified into many types and subtypes.

Major types are
1.   Granulocytes
2.   Monocytes
3.   Lymphocytes

Granulocytes

Granulocytes are further divided into three groups neutrophils, eosinophils, and basophils.

Granulocytes ingest foreign particles such as bacteria and hence are phagocytic in nature.

These cells are known is granulocytes because of the granules of enzymes present in them which digest foreign invaders.

Neutrophils are the most prevalent and can ingest around 5 to 10 bacteria in their lifetime.

Another type of cells eosinophils are involved in the allergic reaction and can attack parasites.
For example worms.

Basophils releases histamine which triggers heparin and prevents blood from clotting.

Monocytes

Monocytes are classified into two groups which are dendritic cells and macrophages.

Dendritic cells mark out foreign bodies that need to be destroyed.

Macrophages are also antigen presenting cells and live longer than neutrophils.

Lymphocytes

These cells regulate the immune system and are divided into two classes B lymphocytes and T lymphocytes.

B lymphocytes

B lymphocytes release Y shaped antibodies that bind to microbes or the cells of the body that become infected.

Antibodies are y shaped proteins that can either neutralize microbes or mark out it for attack by another type of lymphocyte known as T lymphocytes.

T lymphocytes

T lymphocytes are further divided into four subtypes which are

1.  Helper T Cell which releases cytokines and directs the response of other WBCs.

2.  Natural killer T cells release molecules that kill viruses and foreign invaders.

3.  Memory T cells are present when your body suffers from an infection.

4.  Regulatory T Cells regulates other T cells from targeting the body,s own cells.

Fixed leukocytes

Some WBCs when migrates into tissues they take up permanent residence at that location. These cells are named on the basis of tissues in which they settle in.

Examples
Histiocytes
Kuffer cells
Dendritic cells
Mast cells
Microglia.

Disorders

Disorders of white blood cells occur due to three reasons which are when the WBC count is too low or high or when the cells or not functioning properly.

The disorder occurs in neutrophils and lymphocytes are the most common.

Neutropenia

This term is used for low numbers of neutrophils in the blood. Neutropenia may occur due to a genetic disease or due to toxins, and viruses.

Schwan Diamond syndrome

This disease is inherited diseases that occur due to the pancreas dysfunction and congenital neutropenia.

This disease is characterized by a low number of neutrophils in the blood due to insufficient production.

Kossmann syndrome

In this disorder, blood lacks neutrophils because of they do not mature properly.

It is also an inherited disorder.

Eosinophilia

In this disease, the number of eosinophils increases in the blood as a result of signals calling for eosinophils production.

Neutrophilia

In this disease, the neutrophils number increases in the blood and it occurs mostly in response to infections or drugs.

Chronic granulomatous disease

In this disorder, the White blood cells are unable to fight efficiently against bacteria, viruses, and fungal infections.

Leukocytes adhesion deficiency

In this disorder, WBCs are unable to produce proteins that travel to the site of infection.

Chediak Higashi syndrome

In this disorder, the body immune system can not store and release some important enzymes.

Symptoms of white blood cells disorder

1.Frequent infection
2.Mouth sores
3.Tooth and gum diseases
4.Delayed wound healing
5.Greasy diarrhea

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