Which cells release antibodies that fight bacterial infections in the body?

One of the key functions of blood is protection. White blood cells are immune system cells. They are like warriors waiting in your blood stream to attack invaders such as bacteria and viruses. When fighting an infection, your body produces more white blood cells.

For infective organisms to enter the body they must first overcome physical barriers such as the skin, nose hairs, mucus, and stomach acid. Once they have passed this first line of defence they can cause infection. Our second line of defence is then the immune system.

There are several types of white blood cells and they have different roles in defending the body against bacterial, viral, fungal and parasitic infections. When they locate an infection, these cells move to the site under attack to destroy the invading pathogen and prevent illness.

(Picture: white blood cells)

Some directly fight intruders. They are attracted towards the infective agents, then surround and engulf them. Once inside the cell, these white cells then release chemicals that break the organism down and destroy it.

Other white cells, called lymphocytes, target attacks in another way, by making antibodies. These cells detect antigens - proteins on the surface of pathogens which are different to the surface markers on the body’s own cells. When lymphocytes identify antigens as not belonging in the body, they produce antibodies against them. This can take a few days, during which time you may feel ill. Antibodies stick to the antigens and make it easier for the other parts of the immune system to identify, destroy and remove infective agents. Memory cells ‘remember’ the antigens from an infection, so that during a second exposure the immune response is faster. White cells respond more quickly, so antibodies are produced sooner, which can stop you from becoming ill again. Lymphocytes can also produce anti-toxins to neutralise toxins released by some pathogens. Antibodies and anti-toxins are highly specific.

Stem cells in the bone marrow are responsible for producing white blood cells. The bone marrow then stores an estimated 80–90% of white blood cells.

When an infection or inflammatory condition occurs, the body releases white blood cells to help fight the infection.

In this article, learn more about white blood cells, including the types and their functions.

Types and function

Health professionals have identified three main categories of white blood cell: granulocytes, lymphocytes, and monocytes. The sections below discuss these in more detail.

Granulocytes

Granulocytes are white blood cells that have small granules containing proteins. There are three types of granulocyte cells:

• Basophils: These represent less than1%of white blood cells in the body and are typically present in increased numbers after an allergic reaction.
• Eosinophils: These are responsible for responding to infections that parasites cause. They also play a role in the general immune response, as well as the inflammatory response, in the body.
• Neutrophils: These represent themajorityof white blood cells in the body. They act as scavengers, helping surround and destroy bacteria and fungi that may be present in the body.

Lymphocytes

These white blood cells include the following:

• B cells: Also known as B-lymphocytes, these cells produce antibodies to help the immune system mount a response to infection.
• T cells: Also known as T-lymphocytes, these white blood cells help recognize and remove infection-causing cells.
• Natural killer cells: These cells are responsible for attacking and killing viral cells, as well as cancer cells.

Monocytes

Monocytes are white blood cells that make up around 2–8% of the total white blood cell count in the body. These are present when the body fights off chronic infections.

They target and destroy cells that cause infections.

Normal ranges

According to an article in American Family Physician, the normal range (per cubic millimeter) of white blood cells based on age are:

AgeNormal rangeNewborn infant13,000–38,0002-week-old infant5,000–20,000Adult4,500–11,000

The normal range for a pregnant women in the 3rd trimester is 5,800–13,200 per cubic millimeter.

High white blood cell count

If a person’s body is producing more white blood cells than it should be, doctors call this leukocytosis.

A high white blood cell count may indicate the following medical conditions:

• allergic responses, such as due to an asthma attack
• those that may cause cells to die, such as burns, heart attack, and trauma
• inflammatory conditions, such as rheumatoid arthritis, inflammatory bowel disease, or vasculitis
• infections, such as with bacteria, viruses, fungi, or parasites
• leukemia

Surgical procedures that cause cells to die can also cause a high white blood cell count.

Low white blood cell count

If a person’s body is producing fewer white blood cells than it should be, doctors call this leukopenia.

Conditions that can cause leukopenia include:

• autoimmune conditions such as lupus and HIV
• bone marrow damage, such as from chemotherapy, radiation therapy, or exposure to toxins
• bone marrow disorders
• leukemia
• lymphoma
• sepsis, which is a severe type of infection
• vitamin B-12 deficiencies

Doctors may continually monitor white blood cells to determine if the body is mounting an immune response to an infection.

White blood cell test

During a physical examination, a doctor may perform a white blood cell count (WBC) using a blood test. They may order a WBC to test for, or rule out, other conditions that may affect white blood cells.

Although a blood sample is the most common approach to testing for white blood cells, a doctor can also test other body fluids, such as cerebrospinal fluid, for the presence of white blood cells.

A doctor may order a WBC to:

• test for allergies
• test for infection
• test for leukemia
• monitor the progression of certain conditions
• monitor the effectiveness of some treatments, such as bone marrow transplants

Conditions affecting the white blood cells

The following are conditions that may impact how many white blood cells a person has in their body.

Aplastic anemia

This is a condition wherein a person’s body destroys stem cells in the bone marrow.

Stem cells are responsible for creating new white blood cells, red blood cells, and platelets.

Evans syndrome

This is an autoimmune condition wherein the body’s immune system destroys healthy cells, including red and white blood cells.

HIV

HIV candecreasethe amount of white blood cells called CD4 T cells. When a person’s T cell count drops below200, a doctor might diagnose AIDS.

Leukemia

Leukemia is a type of cancer that affects the blood and bone marrow. Leukemia occurs when white blood cells rapidly produce and are not able to fight infections.

Primary myelofibrosis

This condition causes a person’s body tooverproducesome types of blood cells. It causes scarring in a person’s bone marrow.

How to raise or lower white blood cell count

Whether or not a person needs to alter their white blood cell count will depend on the diagnosis.

If they have a medical condition that affects the number of white blood cells in their body, they should talk to a doctor about the goals for their white blood cell count, depending on their current treatment plan.

A person can lower their white blood cell count by taking medications such as hydroxyurea or undergoing leukapheresis, which is a procedure that uses a machine to filter the blood.

If a person’s white blood cell count is low due to cancer treatments such as chemotherapy, a doctor may recommend avoiding foods that contain bacteria. This may help prevent infections.

A person can also take colony-stimulating factors. These may help prevent infection and increase the number of white blood cells in the body.

Summary

White blood cells are an important part of the body’s immune system response. There are different types of white blood cell, and each has a specific function in the body.

Certain conditions can affect the number of white blood cells in the body, causing them to be too high or too low.

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