Antibody deficiencies

Antibodies – also known as immunoglobulins (Ig) – are an important component of the immune system. They help protect the body from pathogens and other foreign substances by binding to them. This makes it easier for the immune system to detect and destroy them. 

Antibodies are produced by a specific group of white blood cells (leukocytes) called B lymphocytes or B cells. 

In healthy individuals, B lymphocytes produce five different types of antibodies – IgA, IgD, IgE, IgG and IgM. 

Some antibodies specialize in dealing with certain foreign substances or are found in particularly large numbers in certain parts of the body. For example, IgA antibodies are largely found in the mucus membranes, while IgG and IgM are typically found in the blood. 

If a person has an antibody deficiency, their body doesn’t produce enough antibodies. As a result, their immune system is weakened and they are much more likely to contract infections. 

There are many different types of antibody deficiencies with different causes. These include: 

• Common variable immune deficiency (CVID): With this type of deficiency, the number of IgG, IgA and/or IgM antibodies is too small.
• X-linked agammaglobulinemia (XLA): This is a congenital immune deficiency, in which the body has only very small numbers of all types of antibodies.
• Hyper IgM syndrome: In this case, the body produces insufficient amounts of IgA and IgG antibodies, while simultaneously producing a normal or excessively high number of IgM antibodies.
• Transient hypogammaglobulinemia of infancy (THI): This is a temporary deficiency in antibodies that occurs in babies or small children if there is a delay in their immune systems reaching maturity.

The main symptom of an antibody deficiency is increased susceptibility to infections. In other words, people with an antibody deficiency are ill on an abnormally frequent basis.

Susceptibility to infection can affect the whole body. Individuals may have frequent infections of the airways, tonsils, gastrointestinal tract, skin and urinary tract, as well as middle ear infections. 

There are various possible reasons for a person to have an antibody deficiency. Some deficiencies are only temporary – as in the case of transient hypogammaglobulinemia of infancy, which occurs when the infant immune system matures too slowly.

Other antibody deficiencies last a lifetime – in other words, they are chronic. They are usually caused by a defect in the immune system, such as a reduced number or complete lack of B-lymphocytes, which produce antibodies. 

Another possible cause is B-lymphocytes that have not fully developed. As a result, they are unable to produce all five antibodies, i.e. IgA, IgD, IgE, IgG and IgM. This can lead to a deficiency in certain types of antibodies – for example, a person may have no IgA antibodies.

In most cases, the causes of these defects in antibody production are unknown. For some disorders, however, the reason has been found in genetic information, i.e. the person’s genes. For example, it is known that some cases of variable immune deficiency syndrome are genetically determined. 

In all cases of x-linked agammaglobulinemia, the cause is genetic – due to a missing gene on an x chromosome, the B lymphocytes fail to mature and cannot produce sufficient numbers of antibodies. As women have two x chromosomes, a defective gene on one x chromosome is compensated for by an intact gene on the other. Men have only one x chromosome. As a result, this deficiency occurs only in boys and men.

An antibody deficiency is the most common type of known immune defect. Around one in 12,000 newborns have an antibody deficiency.

The most common form of antibody deficiency is variable immune deficiency syndrome, which occurs in around one in 50,000 people. 

With the exception of x-linked agammaglobulinemia, most antibody deficiencies occur with the same frequency in women and men. 

Depending on which type of antibody deficiency a person has, the symptoms may occur early in life or at a later stage.

Most antibody deficiencies are detected during the first year of life. The most common form – variable immune deficiency syndrome – is only detected later, usually during adolescence or early adulthood. Transient hypogammaglobulinemia of infancy is an exceptional type of antibody deficiency, as it resolves by itself once the immune system has matured. 

The other types of antibody deficiencies remain with a person for the rest of their life and require regular treatment in order to prevent severe infections, such as blood poisoning (sepsis). 

A stem cell transplant – in which the body receives healthy blood stem cells – can cure the disorder in some cases. If successful, the individual can go on to lead a largely normal life. 

If a person frequently contracts infections, this could be a sign of an antibody deficiency.

Frequent infections are not uncommon among small children, who may become ill up to 15 times a year. Susceptibility to infection generally decreases with age. More than three infections a year would be considered abnormally high among adults. 

If an antibody deficiency is suspected – for example, because a person is very often ill – blood tests can be used to assess the functioning and composition of the immune system. For example, specialists in a laboratory can determine how many and which type of antibodies are present in the person’s body and how active they are. 

The precise genetic defects responsible for some antibody deficiencies are known. In these cases, genetic testing can provide a definitive diagnosis.

Most antibody deficiencies are treated using antibodies – also known as immunoglobulins – from healthy individuals.

These antibodies come from plasma and blood donations. Following special preparation, they are either injected under the skin or into a vein every couple of weeks. While this treatment cannot cure the disorder, it can temporarily strengthen the immune system and reduce the risk of infection. 

Broad-spectrum antibiotics can be used to protect the body from bacterial infections. These are substances that help the body fight many different types of bacteria. However, they are normally only used on a precautionary basis if a person is highly susceptible to infection and at an increased risk of developing a severe infection.

For certain types of antibody deficiencies, doctors may recommend a transplantation of blood stem cells (stem cell transplant).

This type of treatment can result in a complete cure. However, it is also associated with high risks. Therefore, patients should always carefully consider the risks and benefits of a stem cell transplant in consultation with their doctor. It is also a precondition that a suitable donor can be found. 

A life-long antibody deficiency can have a major impact on quality of life. Support groups can help people to cope more effectively with their illness. 

You can find suitable self-help offers via a database on the National Contact and Information Point For Encouraging and Supporting Self-Help Groups (NAKOS) website.