Allergies and intolerances - our immune system

A Brief Summary of How Our Immune System Works

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against “foreign invaders.” These invaders are primarily microbes, such as bacteria, viruses, parasites, and fungi, which can cause infections. Because our body provides an ideal environment for many microbes, they constantly attempt to infiltrate it. However, when the immune system misfires, it can lead to undesirable conditions like allergies or autoimmune diseases.

The immune system is capable of recognizing and remembering millions of pathogens, producing secretions and cells to eliminate them. Its success lies in a highly dynamic and intricate communication system. Immune cells coordinate like a swarm of bees, sharing information and triggering responses. When these cells receive an alarm signal, they transform and release powerful messenger molecules.

A healthy immune system can distinguish between the body’s own cells and foreign entities. Normally, it recognizes harmless substances, but when it mistakenly identifies them as harmful, an immune response is triggered. Any substance that provokes this response is called an antigen. Occasionally, the immune system mistakenly attacks its own cells, causing autoimmune diseases. It can also misinterpret harmless substances, like pollen, leading to allergic reactions.

Key Components of the Immune System

The primary lymphatic organs, such as the bone marrow and thymus, produce B-cells and T-cells. B-cells are responsible for producing antibodies that target antigens circulating in the blood. Each B-cell is programmed to produce a specific antibody. For example, one B-cell may create antibodies to fight the cold virus, while another targets the bacteria causing pneumonia. Antibodies recognize antigens by fitting them like a key into a lock, marking them for destruction.

T lymphocytes (T-cells) play a crucial role in identifying and addressing infected cells. They either trigger immune responses indirectly (helper T-cells) or attack infected cells directly (cytotoxic T-cells). Antibodies belong to a group called immunoglobulins (e.g., IgE, which protects against parasitic infections but often triggers allergies).

While this overview provides a glimpse into the immune system’s workings, it serves as a foundation for understanding allergic reactions.

The Allergic Reaction

Allergic reactions occur when the immune system mistakenly interprets a harmless substance as harmful and launches an attack. Allergies often develop within the first three months of life, though hereditary allergies may begin at birth. Many individuals outgrow allergies over time.

Allergies begin with sensitization, where a foreign substance (allergen) is introduced to naïve T-cells, which transform into helper T-cells. If the helper T-cells become Th2 cells, the immune system records the substance as an allergen. These cells release chemicals (interleukins), prompting B-cells to produce IgE antibodies and recruit mast cells. When IgE binds to allergens, mast cells release chemicals responsible for allergic symptoms.

The next phase, symptomatic reaction, involves allergens binding to IgE antibodies, triggering symptoms in various organs, such as the skin, stomach, or eyes.

Cross-Reactive Allergens

Cross-reactive allergens occur when an antibody binds to epitopes (specific protein sequences) of two different antigens. For instance, birch pollen and certain fruits often share cross-reactive allergens. Heat treatment can sometimes reduce cross-reaction by altering protein structures.

Food Allergies

Food allergies have increased in recent years, likely due to environmental factors like vitamin D deficiency, reduced Omega-3 intake, and obesity. Some research suggests that introducing allergenic foods like peanuts early may reduce allergy risks, though there is no universal prevention strategy. A balanced diet improves overall health and may help mitigate risks.

Milk Protein Allergy

Cow’s milk protein allergy, one of the most common food allergies, primarily affects infants but can persist throughout life. The major allergens in milk are casein fractions and beta-lactoglobulin. Casein is highly heat-resistant, so heat treatment does not eliminate its allergenicity. Cheese-making reduces whey proteins, making aged cheeses potentially safer for some individuals.

Lactose Intolerance

Lactose intolerance occurs when the body cannot produce enough lactase, the enzyme that breaks down lactose into glucose and galactose. While 70% of the world’s population loses lactase activity in adulthood, lactose-free products and fermented dairy options provide alternatives. Lactose intolerance is a digestive issue, distinct from milk protein allergies, which involve the immune system.

Histamine Sensitivity

Histamine, a biogenic amine, plays a vital role in immune responses. It can be produced by the body or introduced through foods. Histamine intolerance occurs when the body cannot produce enough enzymes (e.g., diamine oxidase) to break it down. Avoiding histamine-rich foods and gradually reintroducing them may help manage the condition.

Resources:

M. Hennebelle, H.F.J. Savelkoul, P.L. Weegels, H.J. Wichers, Reader of Food related allergies and intolerances, Wageningen university and researches

https://edepot.wur.nl/198202#page=70

https://www.sciencedirect.com/science/article/abs/pii/S0921448806002574

https://link.springer.com/article/10.1186/s40413-017-0173-0

https://www.sciencedirect.com/science/article/pii/S002203028580789X

http://acta.bibl.u-szeged.hu/21129/1/szef_tudkozl_017_109-120.pdf

https://www.sciencedirect.com/science/article/abs/pii/S0301054615000932