Immune System And Lymph Nodes

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Understanding immune system and lymph nodes

What is immune system?

The immune system is the group of organs, specialised cells, tissues and proteins in your body that act to protect it from harmful substances, germs and even changes within your body that can make you ill.1

There are two fundamental lines of defence comprising the immune system: innate immunity and adaptive immunity. The innate immunity is the first mechanism to fight mainly intruding agents, such as a virus or bacteria, it is rapid, and does not have an immunological memory.

 On the other hand, adaptive immunity, as its name says, is adapted to each specific situation, pathogen that is presented, therefore having immunological memory. With adaptive immunity, there  are antigen-dependent and antigen-specific responses. What this means, is that an antigen, specific structures or chemicals with a pathogen or substance that enters the body, is recognised by specific proteins, called antibodies; something similar to having a specific key to open a specific chain.2 This is of course more complex, and some antibodies can help recognise compounds that are shared between microorganisms or cells.

It’s important to mention that both innate and adaptive immunity act together in a healthy body balancing immediate quick responses to memory protection, and therefore when one of them is out of balance, it can lead to illness or disease.2

What are lymph nodes?

Lymph nodes are part of the lymphatic system, they have traditionally been characterised by three compartments, from the outside to the inside, the cortex, the paracortex and the medulla.3 and it is within these compartments that immune cells are. B and T lymphocyte cells grow, interact with cells that present the antigens mentioned before, and undergo an expansion. The latter is called clonal expansion, in which once cells recognise a specific foreign molecule, they expand as clones to help the body fight or come back to balance.3

The relationship between the immune system and lymph nodes

A robust immune system response requires the coordination of a diverse range of cells present within the host. When the aforementioned antigens are concentrated by lymphatic circulation in the lymph nodes, there is contact with antigen-presenting cells and antigen-responsive cells.4

Lymph is the liquid that circulates throughout the body in the lymph vessels, part of the lymphatic system, carrying white blood cells and taking the information and antigens found to the lymph nodes. 

The lymph nodes are located in many parts of the body, working as filters for foreign substances, which apart from the mentioned bacteria or virus, also includes cancer cells.

When there is a problem, perhaps infection, injury or cancer, you can find swollen lymph nodes, medically referred to as lymphadenopathy (5). Swollen lymph nodes can be painful and in the case of infections, they are usually swollen close to where the infection is occurring, for example in the neck, when the infection is in the ears or throat. In the case of cancer this is a much broader and complex area of study, in which lymph nodes can be swollen due to cancer occurring in other organs or metastasized into the lymph node itself.


The immune system helps us fight foreign elements in our body that can cause us harm and it acts with close connection to other systems within the body. One the closest ones is the lymphatic system, given that lymph nodes are in some sort of way the houses of the different immune cells. It is by carrying the lymph through lymph vessels, and cells from the immune system, that danger can be identified and more immune cells recruited to the site. Other actions follow this identification, in which inflammation is involved, and specialised immune cells can also form, in a clonal way to help the body fight this. Moreover, depending on whatever has been causing this damage, memory T and B cells are formed and called upon when the body encounters the same or similar antigen and requires a response.


  1. How does the immune system work? - - NCBI Bookshelf (  © IQWiG (Institute for Quality and Efficiency in Health Care) Bookshelf ID: NBK279364. April 2020
  2. Marshall, J.S., Warrington, R., Watson, W. et al. An introduction to immunology and immunopathology. Allergy Asthma Clin Immunol 14 (Suppl 2), 49 (2018).
  3. An introduction to immunology and immunopathology | Allergy, Asthma & Clinical Immunology | Full Text (
  4. Willard-Mack CL. Normal structure, function, and histology of lymph nodes. Toxicol Pathol. 2006;34(5):409-24. doi: 10.1080/01926230600867727. PMID: 17067937.
  5. Grant SM, Lou M, Yao L, Germain RN, Radtke AJ. The lymph node at a glance - how spatial organization optimizes the immune response. J Cell Sci. 2020 Mar 6;133(5):jcs241828. doi: 10.1242/jcs.241828. PMID: 32144196; PMCID: PMC7063836.
  6. Lymph Nodes & Cancer | What are Lymph Nodes?

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Aryana Zardkoohi

Master's degree, Tropical disease biology, Liverpool School of Tropical Medicine

Aryana completed a degree in microbiology and clinical chemistry and an MSc in Molecular Biology of Parasites and Vectors. She has several years of experience working as clinical microbiologist at hospitals, and in public health research of tropical diseases.
She is currently undertaking a PhD studying the effects of plant carbohydrates on human gut health. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
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