An antibody deficiency is always a manifestation of the disturbed maturation or function of lymphocytes in the blood. The cells only react inadequately, if at all, to invading pathogens, and the immune system is incapable of maintaining a normal concentration of antibodies in the blood. The consequence is frequently recurring and sometimes life-threatening infections, as well as disturbance of the function of organs.
A typical consequence in particular is an increased susceptibility to bacterial infections. Wound healing and tissue regeneration can be impaired because inflammatory reactions do not die down sufficiently quickly.
A distinction is made between congenital (primary) and acquired (secondary) antibody deficiency diseases.
Primary antibody deficiency
Among the causes of primary antibody deficiency diseases are congenital functional disorders of the antibody-producing B cells and also disturbance of the interaction between the various immune cells, metabolic disorders and genetic defects. To date, around 100 different congenital immune defects have been identified. Their incidence is estimated at 1 per 10,000 inhabitants.
As the patients affected either produce too few antibodies (hypogammaglobulinaemia) or no antibodies of their own at all (agammaglobulinaemia), they must be treated throughout their lives with immunoglobulin preparations.
Primary antibody deficiency diseases are not only manifested in an increased tendency to infection, but, if left untreated, they also lead to an increased risk of the development of autoimmune diseases or tumors.
The regular administration of antibody concentrates (immunoglobulin replacement) can support the antibiotic treatment that is often necessary and prevent severe, recurrent infections. In addition, it helps to maintain vitally important functions of the organs.
Intravenously administered immunoglobulin preparations (IVIG) have proved their effectiveness for many years in raising the serum IgG concentration. The dosage has to be adjusted individually as the antibody deficiency can vary widely in its intensity. Dosages of immunoglobulins between 0.2 and 0.8 grams per kilogram bodyweight are recommended, every three to four weeks. The advantages of this therapy are the immediate bioavailability of the antibodies and a consistently high concentration of IgG in the serum.
Secondary antibody deficiency
A secondary antibody deficiency can occur when the capability of immune cells to react to pathogens and to form antibodies is disturbed due to illness. This form of antibody deficiency is found, for example, in conjunction with a tumor or an autoimmune disease, when the primary disease itself, or the immunosuppressant therapy necessary, permanently impairs the function of the immune system.
Here, too, the causes are usually at cellular level and affect the multiplication and maturation of immune cells or the interaction between different cells. As antibody deficiency is not life-threatening in these cases, or may occur for a limited time, immunoglobulin preparations are administered only for the prevention (prophylaxis) of infections in patients with an increased tendency to infection. The recommended immunoglobulin dose is 0.2 to 0.4 grams per kilogram bodyweight every three to four weeks.
If a patient receives an allogenic bone marrow transplant, this also leads to an antibody deficiency for a while. After the transplantation the body needs a few weeks before the normal production of antibodies restarts and adequate protection from infection is attained. The risk of infection increases after a transplant mainly due to the administration of immunosuppressant drugs necessary to prevent rejection of the transplant.
In this case, the administration of immunoglobulin preparations for a limited time can reduce the tendency to infection and the risk of transplant rejection.