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Interested in learning more about the maternal immune system? Keep reading!

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Which organs & cells make up the immune system?

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The adaptive and innate immune systems involve organs including bone marrow, the thymus, lymph nodes, spleen, gut, and tonsils.

 

White blood cells, a key component of the immune system, develop from stem cells in the bone marrow. There are five general types of white blood cells that have a variety of functions. Neutrophils, the most abundant type of white blood cell are phagocytes (‘phago’ meaning ‘eating’ and ‘cytes’ meaning ‘cells’). These cells engulf potentially harmful foreign invaders and break them down to neutralize the threat of infection.

 

Lymphocytes such as B-cells and T-cells are part of your adaptive immune system. These cells develop throughout your life as you encounter more germs. Lymphocytes can develop into memory cells to prevent reinfection by the same pathogen by recognizing a specific invader and efficiently killing it. Eosinophils are normally present in low levels in the blood and increased levels are associated with parasitic infections. Monocytes can differentiate into several different cell types that are involved in identifying foreign invaders and organizing a systemic immune response by communicating with other cells such as lymphocytes. Basophils are activated during an allergic response.

 

All these cells are found in the blood and different tissues, and are constantly surveying the body for pathogens or unhealthy cells to help prevent you from getting sick, and promote recovery from an illness like a cold or the flu. These cells work together by sending signals to each other to help organize an effective immune response against foreign organisms.

 

• Bone marrow is a spongy tissue inside bones where white blood cells grow and develop.

 

• The thymus, situated just above the heart, is where a specific type of white blood cells called T-cells develop.

 

• Lymphatic vessels are a network that span the entire body, like the blood stream, but they carry white blood cells to immune organs. They are also connected to the circulatory system.

 

• Lymph nodes are very small bean-shaped organs that connect lymphatic vessels. They are found all around the body and are a meeting point for white blood cells to communicate and activate other cells to attack the foreign invader. 

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How does the immune system protect the body from infection?

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The immune system consists of two parts that work together to protect the body:

 

     1. The innate immune system

 

We are all born with an innate immune system, which is made up of different types of chemical and physical barriers to protect the body against disease. Examples of these barriers include parts of the body that interact with the outside world (e.g. skin, stomach) and parts of the body that create an environment that prevents germs from causing an infection (e.g. the vaginal environment is an acidic barrier against infection).

 

The innate immune system consists of special white blood cells called phagocytes. These cells engulf potentially harmful foreign invaders and break them down to neutralize the threat of infection. If the innate immune system needs to recruit more white blood cells to a particular area in the body to fight off infection, it will signal the adaptive immune system for more support.

 

     2. The adaptive immune system

 

The adaptive immune system develops throughout your life, as you are exposed to more germs. After the adaptive immune system has interacted with an invader, it is able to remember that invader in the future, and can successfully attack it to prevent recurring infection. For example, you can only get the chicken pox once because your cells recognize and attack the infection if you ever come into contact with it again. More specifically, memory immune cells have specific receptors that match the proteins on pathogens the body has previously encountered, meaning the body sends off an alarm if it ever comes in contact with it again to mount a highly organized and efficient immune response.

 

However, some germs like viruses that can cause colds are able to mutate quickly, meaning that the body is not able to recognize them as a previous invader and cannot kill them as quickly. As a result, you are more likely to get re-infected by the same invader.

 

Antibodies are an essential component of the adaptive immune system: they are proteins found in the blood that bind to harmful pathogens, effectively neutralizing them and helping the body recover. During an infection immune cells called B-cells secrete many antibodies into the blood that attack the organism causing the infection. They also stimulate the ‘eating cells’ called phagocytes to engulf and breakdown pathogens. They are extremely effective and efficient at fighting disease because they are produced in large amounts and have a region that has a high affinity to the foreign organism so they can quickly recognize and neutralize the destructive invader. 

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How do vaccines work?

 

The purpose of vaccines is to prevent people from getting sick from a specific disease before they come into contact with it. Vaccines contain weakened or dead invaders that would normally cause you to become sick, but instead, stimulate antibody production from B-cells. The antibodies remain in your blood so that if you are ever exposed to the invader in the future, they will quickly recognize and kill the pathogen so you don’t become ill.

 

There are four different types of vaccines:

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• Live-attenuated vaccines

• Inactivated vaccines

• Toxoid vaccines

• Subunit, recombinant, polysaccharide, and conjugate vaccines

 

Live attenuated vaccines contain the live weakened pathogen and result in long-lasting immunity after one or two doses because it closely resembles the natural germ. An example of live-attenuated vaccine is measles mumps and rubella (MMR). Inactivated vaccines such as the flu shot contain the dead invader, and boosters are required to ensure immunity is maintained throughout one’s lifetime. Toxoid vaccines are designed to promote immunity against the parts of the pathogen that induce disease. For example, the tetanus bacteria produce a dangerous toxin that damages the nervous system and the vaccine induces immunity against the toxin. Subunit, recombinant, polysaccharide, and conjugate vaccines such as hepatitis B or HPV contain a specific portion of the virus such as a sugar or protein that stimulates a strong immune response. Booster shots may be required, and patients with immune deficiencies or illnesses can usually receive these vaccines as they do not contain the whole virus.  

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Disclaimer

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Every woman and every pregnancy is unique. Pregnant women should speak to their healthcare provider to ensure maternal and fetal safety. This article is meant to provide readers with current information and opinions. All medical and treatment decisions should be discussed with your healthcare provider.

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This article was written by Claire Mazzia and Dr. Kelsey McLaughlin and edited by Dr. Kelsey McLaughlin and Dr. Melanie Audette​.

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