Deficiency of Bcellsleadsto “hypogammaglobulinemia”,agammaglobulinemia etc. diseases associated with antibody deficiency.
Generally immune system in children starts producing antibodies by the time the maternal immunoglobulins acquired through placenta and breast milk exhausts. But some children fail to produce antibodies due to deficiency of B cells.
Since all antibodies are secreted by B-lymphocytes (B-cells), any disease that harms the development or function of B-cells reflects in the production of immunoglobulins.
Even though immunesystem is functional, people with immunoglobulin deficiency syndromes become ill more often, because most of the invading microbes for example streptococci, meningococci, and Haemophilus influenzae escape attack by immune cells through encapsulation.
Since immunoglobulins are capable of binding to the encapsulate microbes, their survival becomes difficult in people with normal immunoglobulin production. This kind of protection is lost in people with B cell deficiency.
Patients with immunoglobulin deficiencies may also show a bad response to the attenuated version of the polio virus vaccine. They are also prone to some viral infections, including echovirus, enterovirus, and hepatitis B.
Two types of immunodeficiency diseases (1) Primary congenital and (2) secondary acquired immunodeficiency are found associated with B cells deficiency.
Congenital immunodeficiency is present at the time of birth, and is the result of genetic defects. Even though more than 70 different types of congenital immunodeficiency disorders have been identified, they rarely occur.
Congenital immunodeficiencies may occur as a result of defects in B lymphocytes, T lymphocytes, or both. But primary congenital immunoglobulin deficiency syndromes are the most prevalent type of immunodeficiency disorders occurring due to defective B-cells or antibodies. They account for 50% of all primary immune deficiencies. Following are some of the examples for congenital immunodeficiency disorders.
(1) Bruton’s agammaglobulinemia, also known as X-linked agammaglobulinemia is an inherited disease. The defect is associated with the X chromosome; as a result this disease is seen more frequently in males than females. The defect results in a failure of B-cells to mature and secrete immunoglobulins.
(2) Selective IgA deficiency is an inherited disease that occurs 1 in 700 of population. It is due to failure of B-cells to switch from making IgM, the early antibody, to IgA. Although the number of B-cells is normal, and can make all other classes of antibodies, the amount of IgA produced is limited. This results in more infections of mucosal surfaces, such as nose, throat, lungs, and intestines. Since this deficiency is asymptomatic, it can be identified only by chance.
(3) Ig heavy chain deletion is a genetic disorder in which, part of the antibody molecule is not produced. It results in the loss of several antibody classes and subclasses including most IgG antibodies and all IgA and IgE anti-bodies.
(4) Selective IgG subclasses deficiency is a group of genetic disease. Due to defects in B cell maturation, the process of class switching fails to take place in Ab gene, ensuing failure in the mechanism to produce some of the subclasses of IgG.
(5) IgG deficiency with hyper-IgM is a disease that results when the B-cell fails to switch from IgM making to IgG. This disease is the result of a genetic mutation.
Secondary Acquired Disorders:
Secondary acquired disorders occur in normally healthy individuals due to certain under lying diseases including HIV infection or failure to thrive. But it often occurs as a complication of other conditions and diseases.
For example, the most common causes of acquired immunodeficiency are malnutrition, some types of cancer, and infections. Once the disease is treated, the immunodeficiency is reversed. For example
(1) Transient hypo gamma globulenemia of infancy is a temporary disease of unknown cause. Hypogammaglobulinemia is characterized by low levels of gamma globulins (antibodies) in the blood. During the disease period, patients have decreased levels of IgG and IgA antibodies.
(2) Common Variable Immunodeficiency (CVI) can develop at any age of an individual. The underlying cause for CVI is not known, but it is clear that there is a defect in the T cell – B cell cooperation that is needed for B cells to differentiate into plasma cells.
This results in very low levels of antibody in the circulation but a normal B cell count. The imbalance of T cell and B cell function can result in a loss of self tolerance ensuing autoimmune disease.
Consequence of Immunoglobulin Deficiencies
Complications of antibody deficiency include acute infections, due to unusual organisms such as mycoplasmas, and long term complications such as bronchiectasis, fungal infections, granulomas, lymphoma, recurrent sinusitis, giardia, Cryptosporidia, colitis, gastric carcinoma, hepatitis, autoimmune haemolytic anaemia, immune thrombocytopenic purpura, acute enteroviral meningoencephalitis etc.
1. Serum immunoglobulin concentrations, including IgG subclasses.
2. When serum immunoglobulin concentrations are greatly depressed, confirmatory tests are not always necessary.
3. Functional antibody responses to immunisations, common bacteria and red cell antigens may be required.
4. Plasma B lymphocyte sub-populations concerned with antibody production.
1. Prompt antibiotic treatment, constant prophylaxis.
2. Regular supply of immunoglobulins intravenously.
3. Subcutaneous immunoglobulin supply is an alternative to intravenous administration.
4. Higher doses may be needed in patients with known lung damage.
5. Side effects (which include headache, nausea, chills, and fever) can be reduced by lowering the rate of infusion.