Immune System


We are surrounded by billions of bacteria and viruses. For many of them, the human body is like a walking smorgasbord, offering almost unlimited resources that they can use as a source of energy and for their reproduction. Luckily for us, getting into the human body is not an easy task.

From the point of view of these tiny organisms, humans are a bit like a fortress. The skin is thick and very difficult to penetrate. In addition, the skin produces a variety of substances that harm the 'invaders'. The openings, such as the eyes, nose and mouth, are protected by fluids and viscous mucus that capture harmful attackers. The respiratory system has mechanical protection in the form of airway epithelial cilia, tiny hairs that remove particles. Intruders that get as far as the stomach will encounter highly acidic gastric juice, which will kill most of them.

However, despite our fantastic defences, dangerous intruders can still get through. Some get in with our food and others can slip in through the nose. And as we are all well aware, many things can damage our skin. Every day there is some sort of scrape or cut and every time this happens, we are exposed to the intrusion of bacteria or viruses. So what magical force keeps us healthy most of the time?

When we injure ourselves (cut or scratch ourselves) and intruders enter our body, our cells may get destroyed. The dying cells trigger an automatic response called inflammation, which includes vasodilatation of blood vessels and increased blood flow. Inflammation for the body is the equivalent of a burglar alarm. When this alarm goes off, it pulls huge numbers of defence cells to the site of damage. The increased blood flow helps the defence cells get to the site. This is also responsible for the onset of redness and swelling at that site.

Our Defence: Cells of the Immune System

Our defence cells are more commonly referred to as immune system cells. They are part of our highly effective defence force called the immune system. Immune system cells work together with a variety of proteins to seek out and destroy anything foreign and dangerous when it invades our body. It takes some time for the immune system cells to activate, but once they start working at full force, very few hostile organisms would stand a chance.

Antigen Presentation

Antigen presentation - a term encompassing immune mechanisms that involve "showing" the antigen to T lymphocytes with the participation of MHC molecules. The main goal of antigen presentation is to develop a specific response to a given antigen. It is characteristic that antigens are not presented in their original (native) form, but in a processed form.

There are three classes of MHC that differ in their functions:
    • MHC class I – are found on all nucleated cells and participate in defense against intracellular pathogens.
    • MHC class II – occurs on antigen-presenting cells
    • MHC class III – are various molecules unrelated to the antigen presentation process.
They were first designated as probable presenting molecules due to their location between the MHC class I and MHC class II genes (which was rejected after further genome studies). While there are outstanding structural similarities between classes I and II, class III MHCs are not similar to the other two classes or to each other.

Human MHCs are called HLA – human leukocyte antigens.

Diversity of antigen presentation, mediated by MHC* classes I and II, is attained in three ways: (1) the MHC's genetic encoding is polygenic, (2) MHC genes are highly polymorphic and have many variants, (3) several MHC genes are expressed from both inherited alleles.

* MHC – major histocompatibility complex – a set of proteins responsible for the presentation of antigens to T lymphocytes. They owe their name to the fact that they were discovered as the first and most important proteins determining the maintenance or rejection of the transplant, therefore responsible for the compatibility of donor and recipient tissues.
  • Class I of MHC molecules, which present antigens to Tc cells (cytotoxic lymphocytes), are involved in defense against intracellular pathogens, e.g. viruses. If such an antigen is recognized as foreign, the presenting cell will be killed, because its presence on the MHC class I molecule indicates the existence of the pathogen inside the cell. When killing a cell, a Tc lymphocyte usually also kills the parasite inside it. It can be said that in this way the individual (cell) is sacrificed for the common good (whole organism).
  • Class II of MHC molecules that present antigens to Th cells  (helper lymphocytes) do not cause the death of the antigen-presenting cell. In this case, this cell starts secreting cytokines that stimulate the Th lymphocytes. Th lymphocytes are important cells that regulate the immune response. Thanks to this, class II of MHC molecules participate in the stimulation of other cells via helper T cells.
  • Cross-presentation is a mechanism that enables the stimulation of both Th cells and Tc cells, involving both class I and class II of MHC molecules. However, it is not a simple combination of the two previously mentioned types of antigen presentation. It occurs in a characteristic way with the participation of specific cells that present antigens simultaneously on MHC of both classes and are not killed by Tc lymphocytes.

2 Macrophages and dendritic cells belong to the so-called antigen presenting cells.

Structure of the Immune System

The immune system is a very complex structure consisting of cells, tissues and organs that work together to protect (defend) our body against "foreign" invaders . . .

How the Immune System Works?

It is one of nature's most fascinating inventions. It easily protects us against billions of bacteria, viruses and pathogens. We don't realize that the immune system . . .


Immunodeficiencies are disorders of the immune system that are characterized by a reduced or lack of ability to . . .

Maintain Healthy Immune System

If we are not dealing with an immune system disease, it is usually enough to use a few simple . . .


The European Medicines Agency (EMA) has approved gene therapy for the treatment of severe combined immunodeficiency due to adesine deaminase deficiency (ADA-SCID), which is the result of a genetic mutation - reports New Scientist. You can read about gene therapy, what it is and its prospects, on the website News Medical Life Sciencies


Source: Memorial Sloan Kettering Cancer Center Library / LibGuides / COVID Impacts / Immune Dysfunction

Detailed information and resources on the long-term health consequences of COVID-19 infection and the broad social impacts of the COVID-19 pandemic.

One of the most concerning long-term effects of COVID-19 is the dysregulation and dysfunction of the immune system.


Source: Nutrients Authors: van Steenwijk H, Bast, A and de Boer A.

Beta-glucans derived from mushrooms are bioactive long-chain polysaccharide compounds, insoluble in water and with immunomodulatory properties. Knowledge of the action and functions of beta-glucans, which have been used in traditional medicine for centuries, is developing thanks to modern immunological and biotechnological methods.


Source: Oncology Reports; Authors: Hiromi Okuyama Akira Tominaga, z Laboratory of Immunology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan

Spirulina lipopolysaccharides inhibit tumor growth in a Toll-like receptor 4-dependent manner by altering the cytokine milieu from interleukin-17/interleukin-23 to interferon-γ