These proteins save your life

What are immunoglobulins?

Immunoglobulins, also known as antibodies, are essential proteins of the immune system. These proteins are produced by specialised white blood cells, called B lymphocytes and plasma cells. 

They play a central role in the defence against pathogens by specifically recognising, binding to and neutralising foreign substances such as viruses, bacteria, toxins or pollen. This specific capability arises because immunoglobulins are effectively programmed to target certain components of a pathogen, serving as an effective protective shield for health.

Production of immunoglobulins begins when B lymphocytes (B cells) encounter antigens – i.e. foreign structures. These antigens can be proteins, lipids or carbohydrates. After the initial contact, B cells develop into plasma cells that secrete matching immunoglobulins in large quantities. These antibodies bind specifically to the antigens, much like a key fits into a lock.

Immunoglobulins have a Y-shaped structure. With the „arms" of the Y they attach to antigens, while the „stem" interacts with the body's defence cells. This allows pathogens to be directly neutralised or destroyed by other components of the immune system.

What function do immunoglobulins have in the body?

On first contact with a pathogen, immunoglobulins are newly produced. After recovering from an infection, the immune system stores these antibodies so it can react more quickly if it encounters the same pathogen again. This principle underlies vaccinations, in which weakened or inactivated pathogens are injected to stimulate the production of specific antibodies.

There are different classes of immunoglobulins, distinguished by their site of action and function. IgA protects mucous membranes, e.g. in the digestive and respiratory tracts. IgG is responsible for long-term immunity and the fight against pathogens in the blood. IgE mediates defence reactions against parasites and is involved in allergies. IgM provides the first line of defence in initial infections.

However, immunoglobulins can also be misdirected and attack the body's own substances. This leads to autoimmune diseases such as rheumatoid arthritis, type 1 diabetes, Crohn's disease or multiple sclerosis, in which inflammation and tissue damage occur.

In summary, immunoglobulins identify antigens and bind to them specifically. They can directly render pathogens harmless or tag foreign bodies and activate other defence cells.

Immunoglobulins also provide long-lasting immunity: they remain stored in the body after an infection and enable a rapid response to reinfection.

What is immunoglobulin A or IgA?

Immunoglobulin A (IgA) offers protection at the body's entry points. This special class of antibodies forms the first line of defence by neutralising intruders such as viruses and bacteria directly at the body's entry points before they penetrate deeper and can cause infections.

IgA is found mainly on the mucous membranes of the nose and throat, in the digestive tract and in the genital area. It is also present in tears, saliva and breast milk. IgA is transferred from the mother to the infant via breast milk. These passive antibodies provide the newborn with protection against infections, especially in the first months of life when the infant's own immune system is not yet fully developed.

IgA binds to pathogens, neutralises them and prevents them from penetrating the mucosa. It protects mucous membranes from damage and supports their function as a physical barrier. IgA works together with other components of the immune system to ensure an effective defence.

A low IgA level may indicate a weakened immune defence, leading to recurrent infections. IgA values can also be helpful in diagnosing autoimmune diseases, as these are often associated with changes in antibody production.

What is immunoglobulin M or IgM?

Immunoglobulin M (IgM) is the immune system's "first responder". It is produced immediately after contact with pathogens and provides a rapid and effective defence in the early phase of infection. 

Interestingly, IgM is partly present in the blood even without contact with antigens and thus functions as part of the nonspecific immune response. IgM is the largest immunoglobulin and consists of five antibody units linked into a pentamer. This structure allows multiple antigens to be bound simultaneously and effectively neutralised.

IgM plays a crucial role in activating the complement system, a component of immune defence that supports the destruction of microorganisms. After the acute phase of infection, IgM concentration falls and the longer-lasting IgG antibodies take over the immune response.

Because IgM antibodies are produced quickly after infection, their presence is often used to diagnose acute infectious diseases. A decrease in IgM levels indicates the end of the acute infection phase and the transition to a specific immune response mediated by IgG.

What is immunoglobulin E or IgE?

Although IgE accounts for only a very small proportion (about 0.1 percent) of the total amount of antibodies in the body, its function in certain immune responses is of critical importance.

Immunoglobulin E (IgE) is a specialised antibody primarily responsible for the defence against parasites and the triggering of allergic reactions. It plays a key role in protection against microscopic organisms. At the same time, IgE is the main actor in allergic reactions because it induces the release of inflammatory mediators such as histamine from mast cells. Despite its low quantity in the blood, IgE has an important role in immune defence and in the diagnosis of allergic diseases and parasitic infections.

It binds to the surface of pathogens and helps activate the immune system to destroy parasites. In allergic sensitisation there is an overproduction of IgE, which attaches to mast cells and basophils. Upon re-exposure to the allergen, IgE triggers the release of histamine and other substances responsible for the typical symptoms of allergies, such as itching, swelling, breathing difficulties and skin rashes.

Blood IgE levels are often measured to diagnose allergic diseases and determine the severity of an allergy. A high IgE level is often an indicator of allergic reactions such as hay fever, asthma, food allergies or insect venom allergies. An elevated IgE level can also indicate a parasitic infection, as IgE is central to fighting these microorganisms.

What is immunoglobulin G or IgG?

Immunoglobulin G (IgG) is the most common and widespread class of antibodies in the human body. It plays a central role in protection against infections and is particularly important for the so-called "immune memory" – the immune system's ability to remember pathogens it has already fought and to respond quickly and specifically on re-exposure.

IgG accounts for about 60 to 80 percent of all antibodies in the blood. B cells are activated by contact with pathogens and then produce IgG antibodies that are specifically directed against the pathogen's antigens (proteins or structures).

An important feature of IgG is that B cells become memory cells after the first infection. These "B memory cells" remember the specific antibodies and are able to reproduce them on re-exposure to the same pathogen quickly. This mechanism is a fundamental part of the immune response and allows a faster and more effective fight against repeated infections.

IgG also plays an important role during pregnancy. IgG antibodies are transferred from the mother to the embryo via the placenta, protecting the newborn for a period after birth. This "nest protection" lasts only for the first three months after birth, after which the infant's immune system must produce its own antibodies.

IgG plays an important role in the fight against chronic infections, such as hepatitis or chronic inflammatory diseases. In such cases, IgG production may remain active for extended periods to help control the disease.

What side effects can immunoglobulins have?

Immunoglobulins can, like any medicine, cause side effects. These do not occur in every patient, and the type and frequency of side effects can vary depending on the pharmaceutical form (e.g. infusion, injection). Common side effects include allergic reactions (symptoms such as rashes, itching and redness), circulatory reactions (drop in blood pressure, breathing difficulties and chills), general malaise (headache, nausea and vomiting, joint pain or mild back pain), and fever (especially after the first dose or after prolonged infusions).

Very rare or isolated side effects include anaphylactic shock, a potentially life-threatening allergic reaction requiring immediate medical attention. Symptoms include breathing difficulties, circulatory collapse and severe swelling.

In rare cases, immunoglobulins can trigger destruction of red blood cells, leading to anaemia. This can be accompanied by symptoms such as fatigue, weakness, dizziness, headache, palpitations, tinnitus, shortness of breath or jaundice.

It is important that patients receiving immunoglobulins pay close attention to these possible side effects and seek medical help immediately if unusual symptoms occur. Reactions to immunoglobulins can vary greatly between individuals, which is why close medical monitoring is required.

What to do if immunoglobulin values are altered: the best tips

• If altered immunoglobulin values are detected, it is important to make an early diagnosis to identify any underlying conditions. Regular monitoring of immunoglobulin levels is crucial to track the course of the disease and take therapeutic measures in good time.
• In acquired immunoglobulin deficiency, the underlying condition should always be treated. For example, patients with diabetes mellitus may require insulin therapy, or hypothyroidism may require hormone replacement therapy. Treating the underlying disease can help normalise immunoglobulin levels.
• In congenital immunoglobulin deficiency, lifelong replacement with immunoglobulins is usually required. These can be administered intravenously or subcutaneously to compensate for the lack of antibodies and support the body's defences.
• People with an immunoglobulin deficiency should take special care to prevent infections. They should avoid contact with sick people, intensify hygiene measures and consult a doctor early if signs of infection appear. It may also be helpful to be vaccinated against certain diseases to reduce the risk of infection.
• If an infection occurs, the doctor should prescribe antibiotics or other appropriate medications if necessary. It is important to treat infections quickly to avoid complications, especially in patients with antibody deficiency disorders.
• If a monoclonal hypergammaglobulinaemia is diagnosed, it is essential to determine the cause. Investigations such as bone marrow analysis, urine tests or imaging may be used. Once the underlying disease is known, appropriate treatment is initiated.
• When vaccinating people with altered immunoglobulin values, note that administration of immunoglobulins can impair the effectiveness of live vaccines. It is recommended to wait three months after receiving immunoglobulins before administering live vaccines. There are no such restrictions for vaccines with inactivated pathogens or toxoids.
• During pregnancy and breastfeeding, immunoglobulins should only be given after careful consideration of the benefit-risk balance by the treating physician. Although no harmful effects on the child are expected, the use should always be discussed with the doctor.
• It is important to inform the doctor about all medications being taken to avoid possible interactions. Immunoglobulins can, for example, affect the efficacy of vaccines. Other medications, such as certain blood pressure or diabetes drugs, should also be adjusted in consultation with the doctor.
• A balanced diet and a healthy lifestyle can additionally strengthen the immune system and help support recovery. Regular exercise, sufficient sleep and stress reduction are also important factors for a healthy immune system.
• Patients with antibody deficiency or other immune disorders can seek psychological support to better cope with the challenges of the condition. Managing chronic health problems can be stressful, and psychological counselling can help improve quality of life.
• When immunoglobulin values are altered, close collaboration with an immunologist or other specialists is important to ensure the best possible treatment. Regular consultations and therapy adjustments can help stabilise immunoglobulin levels and prevent complications.

Whether they act for the first time during an infection or prepare the immune system after vaccination, the ability of immunoglobulins to recognise and counter threats in a targeted way makes them a fascinating and complex defence system.