Primary Immunodeficiency (PI) : Treatments, Part 2

by National Institute of Health

(Page 6 of 13)

Another treatment option, for children with a specific form of SCID who don't have a suitable bone marrow donor, is enzyme replacement therapy. About 15 percent of all cases of SCID are due to lack of the enzyme known as adenosine deaminase (ADA). This type of SCID can be partially treated with regular injections of the missing enzyme. For treatment, ADA is linked to a chemical, polyethylene glycol (PEG), which protects ADA from being quickly eliminated from the bloodstream.

For many people with antibody deficiencies, antibody replacement therapy can be a lifesaver. The patient receives regular infusions or injections of immunoglobulins, or antibodies, that have been removed from the blood of healthy donors and purified. Immunoglobulins from thousands of donors are pooled so that each batch contains antibodies to many different types of germs. Because purification removes most IgM and IgA, the product consists almost entirely of IgG. It is known as gammaglobulin, immunoglobulin, or immune serum globulin.

Taken regularly and in large doses, gammaglobulins can boost serum immunoglobulins to near normal levels and eliminate most infections. If treatment begins early enough, it can prevent lung damage from pneumonia.

Immunoglobulin is administered either intramuscularly or intravenously. Intravenous immunoglobulin (IVIG) is usually preferred because it can be given in large doses, it is fast-acting, and it avoids the pain associated with large intramuscular injections. Infusions of IVIG take two to four hours and are administered every three or four weeks, either at home or in an outpatient clinic.

Injections of cytokines, which are natural chemicals produced by immune cells, are another new way to treat immune deficiencies. For example, the symptoms of Chronic Granulomatous Disease can be traced to faulty phagocytes; phagocytes can be activated with injections of a natural or synthetic product of immune cells called gamma interferon.

In some immune deficiencies, the numbers of neutrophils may be reduced either because they are under attack or are not produced in normal numbers. In certain cases, this problem can be offset by the injection of growth factors. These growth factors increase the production of neutrophils. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a natural chemical that boosts the development of blood cells, including the white blood cells known as granulocytes and macrophages. Another granulocyte colony-stimulating factor (G-CSF), is also helpful in raising levels of granulocytes.

Important Precautions

Children with PI diseases, especially those with defective T cells, X-linked agammaglobulinemia, and ataxia telangiectasia should not receive live virus vaccines, such as the oral polio, measles, and chicken pox (varicella) vaccines. It is not even safe to give live virus vaccines to children suspected of immunodeficiency until a definitive diagnosis is rendered. There is a risk that such vaccines could cause serious illness or even death. Moreover, blood transfusions should not only be free of infectious viruses (e.g., hepatitis or cytomegalovirus), but also - for T cell deficient children - irradiated to incapacitate mature donor T cells that might attack the tissues of the recipient and result in GVHD.

Primary Immunodeficiency Diseases: Some Examples

Primary immunodeficiencies are complex diseases. Since each one can be traced to the failure of one or more parts of the immune system, one of the more convenient ways to group them is according to the part of the immune system that is faulty: B cell (antibody) deficiencies, combined T cell and B cell (antibody) deficiencies, T cell deficiencies, defective phagocytes, complement deficiencies, deficiencies/cause unknown.

B Cell (Antibody) Deficiencies

More than half of all PIs are caused by a lack of infection-fighting antibodies (immunoglobulins). The person has either too few antibody-producing B cells or B cells that don't work properly.

In some disorders, the B cells make almost no antibodies, leaving the person susceptible to a wide range of infections. In others, the B cells make some antibodies, but not enough to give strong protection. In yet other conditions, the B cells fail to make special subsets of antibodies, creating a risk for just certain kinds of infections.

X-Linked Agammaglobulinemia (XLA) youngsters make no antibodies at all (a = without, gammaglobulin = antibodies, emia = in the bloodstream). These patients have few or no mature B cells or antibody-secreting plasma cells.

It is called X-linked because the mutated gene responsible for the disease is located on the X chromosome. (This gene encodes an enzyme necessary for B cell development.) As an X-linked disease, XLA affects only males.

For their first few months, baby boys who have inherited XLA are healthy, protected by IgG they received from their mothers via the placenta before birth and in the breast milk after birth. As the mother's IgG fades, however, the baby develops a steady stream of infections.

They get infections caused by bacteria that would normally be controlled by antibodies - ear infections, sinus infections, eye infections, skin infections, and pneumonia. They can also develop encephalitis, meningitis, or blood poisoning. Antibiotics clear up one infection, only to have another start up soon.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.