White Blood Cells: An Immunology Review

nursing students looking through microscope studying white blood cells

Jump to Sections


  1. White Blood Cell Components
  2. Components of WBC Expanded
  3. WBC Development: The Final Stage
  4. The Lymphatic System
  5. Newborn Jaundice & WBC

In this post, we’re coving immunology, mainly focusing on the white blood cells (WBC), which are considered the body’s military base or police department.

Within the military, different positions are particularly tasked with responsibilities, ranging from detectives, investigators, patrol officers, sergeants, and captains. Similarly, white blood cells also have these types of components, which we will all go through thoroughly to properly identify their jurisdictions and functions.

White Blood Cell Components

First, we’ll have a quick introduction of each key player and elaborate later on. What are the primary components of white blood cells?

  1. Neutrophils – involved in the body’s inflammatory response that composes 55% – 70% of the entire white blood cell army.
  2. Monocytes – made up of macrophages and phagocytes. Monocytes, like Pac-man, are five to six percent of the body’s white blood cell count and are responsible for devouring bacteria and viruses.
  3. Lymphocytes – known as the body’s natural killers or mercenaries, lymphocytes are about 30% – 40% of white blood cells. There are two types of cells involved with lymphocytes, namely:
  • B cells – also known as plasma cells that shoot antibodies, labeling the invader as a foreign element that needs to be destroyed by other cells like the T cells
  • T cells – tagged as the mercenaries or natural killers of the body, T cells are divided into two groups: CD4 cells and CD8 cells. The CD4 cells are the cells that HIV overrides. On the other hand, the CD8 cells attack the antibodies marked by the B cells, killing the infecting bacteria.
  1. Eosinophils and Basophils – make up one to two percent of white blood cells. The eosinophils and basophils are mainly responsible for the body’s allergic response.

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The Thymus Gland

Aside from the five important components of white blood cells, we will also cover the thymus – a critical gland in the final stage of white blood cell development. The thymus is like a boot camp for most of the blood cells, mainly the T cells’ last training phase.

Once the white blood cells are created, they are stored in the barracks (the spleen). The spleen not only serves as the storage for WBCs, but it also is the graveyard for hemoglobin and platelets.

White blood cells “patrol” along the highways of the lymphatic tissue and the bloodstream. So if there are invaders, the white blood cells will easily be prompted and will be activated to take on whatever threat is present in the system. 

For this reason, a blood culture is taken whenever a person is deemed sick. This determines what kind of infection the body has.

Components of White Blood Cells Expanded

1. Neutrophils

If inflammation occurs within the body, you can count on neutrophils to act on them. Neutrophils make up 55% up to 70% of the body’s WBC army. Under this category, there are two different types: the segmentals and the baby bands.

Segmentals are the upper-class men in the army tasked to fight off bacteria and viruses that cause infection, leading to inflammation. On the other hand, the baby bands are immature segmentals also created to ward off the threat inside the body, but are too small and underdeveloped to do so.

2. Monocytes

Monocytes make up five to six percent of white blood cells and are divided into macrophages and phagocytes. Monocytes are the patrol officers inside the body that go around the system, destroying and devouring viruses and bacteria that can cause infections.

While macrophages and phagocytes are categorically the same regarding responsibilities, macrophages are more elite than phagocytes (much like a sergeant to a cop). You can consider monocytes as Pac-man because of their nature of “eating up” harmful threats.

3. Lymphocytes

The lymphocytes are the main patrollers of the lymphatic tissues and the bloodstream, making up 30% to 40% of the body’s WBCs. These patrollers are known as the natural killer cells because of their Terminator-like properties that will eliminate any intruder in their path. The lymphocytes are composed of the B cells and the T cells.

The B Cells

As mentioned above, the B cells are the plasma cells that are like little plasma guns which shoot tags (antibodies) all over an invading bacteria, marking it and prompting the other white blood cells to get rid of it. 

To explain further, let’s create a simple scenario:

Imagine robbers invading a bank. The other white blood cells (segmentals, macrophages, T cells) show up like a SWAT team. To differentiate the robbers from the hostages, the B cells will “spray” or mark them as a threat using antibodies. Because of this action taken by the B cells, the SWAT team will immediately recognize who to eliminate.

This scenario is a nice way to interpret how B cells work. An invading organism comes in, the B cells spray it with antibodies, alerting the other cells what to attack.

The T Cells

The T cells, on the other hand, are the killers of viruses and bacteria. There are two divisions of the T cells: CD8 and CD4. The CD4 is the component that is primarily targeted by the human immunodeficiency virus (HIV), while the CD8 binds directly to the antigen to kill the invading bacteria.

CD8 binds with the antigen the B cells have marked as the “bad guys.” Once spotted, the CD8 cells will pursue the target and wipe them out immediately.

CD4 cells have several responsibilities, namely:

  1. They are the commanding officers or the generals of the army. They call the shots or give orders on what to attack, when, and who should do the attack. So basically, the CD4 cells are in charge of the entire army of white blood cells.
  2. They summon the following WBC components:
  • B cells – plasma cells
  • Lymphocytes – natural killers
  • Macrophages

These summoned mercenaries take orders from the CD4 cells on what to kill or eat.

HIV and the CD4 Cells

When a client has human immunodeficiency virus, the CD4 cells are compromised because the virus attaches itself to the CD4 cells and invades them by sending its DNA inside the CD4 cells. Once HIV has invaded the CD4 cell, it will take over command of the “mothership.”

Like sci-fi films, once the mothership is captured and taken over by threats, the decisions are altered, and control of the entire army is at the mercy of the invaders. This makes HIV smart because instead of destroying the one in charge, it re-hardwires its system through DNA invasion and takes control over the fleet – making HIV a scary virus.

What happens to the army of white blood cells? All these armies (B cells, lymphocytes, macrophages), will still be taking command from the CD4 cell that HIV has now infiltrated. This is why (if some other bacteria or viruses enter the body), the army will not function properly or respond.

4. Eosinophils and Basophils

Eosinophils and basophils are technically similar in targeting allergies. To remember this, think about, “Eww, baso allergies.” Basically, eosinophils and basophils only respond to allergies, which is why about one to two percent of them are in the WBC army.

White Blood Cell Development: The Final Stage

As previously mentioned, the thymus is the area where white blood cells are developed completely; it’s the boot camp where they perfect their skills in warding off harmful elements that can inflict the body. The spleen is the barracks where they are stored and where they wait for further instructions.

Remember that the spleen is not just a storage but also a graveyard for hemoglobin and platelets, it’s also where dying hemoglobin is converted into bilirubin before it’s sent to the liver. 

The liver will put the bilirubin on the bile bus together with cholesterol, eventually driving them out of the body.

The Lymphatic System: The Highway Patrol

White blood cells patrol the lymphatic system and the bloodstream, making it easier for white blood cells to detect threats inside the body. This is why (whenever blood samples are taken and there is an increased level of white blood cells), medical professionals will immediately suspect an infection – bacterial or viral.

The ways to determine increased white blood cells are through blood culture and lumbar puncture to take cerebrospinal fluid.

Newborn Jaundice & WBC

Newborns have a lot of blood and hemoglobin that are broken down in the spleen. This increased hemoglobin level is then taken to the newborn’s liver. 

Since the liver is not big enough to accommodate high bilirubin levels, the bile bus becomes overloaded. As a result, jaundice happens. 

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