Immunoglobulin D deficiency

Immunoglobulin D deficiency (IgD deficiency): Description, Causes and Risk Factors:Alternative Names: Hypoimmunoglobulinemia D, hypogammaglobulinemia D, dysimmunoglobulinemia D, dysgammaglobulinemia D, selective IgD deficiency.ImmunoglobulinImmunoglobulin IgD is the major antigen receptor isotype co-expressed with IgM on the surface of most peripheral B cells in mice and humans. However, the biological role of IgD as B cell receptor (BCR) has remained unclear. Selected immunoglobulin D (IgD) is present in a small amount in human serum, and membrane-bound IgD is a major component of the B-cell antigen. Results from a recent study of IgM-deficient mice suggest that IgD is able to substitute for IgM in most of its functions. However, the phenotype of IgD-deficient mice is virtually normal, except for an impairment of antibody (Ab) affinity maturation.The serum IgD half-life is known to be short, which is probably attributable to its high sensitivity to proteolysis (the hydrolysis of proteins into peptides and amino acids by cleavage of their peptide bonds). IgD antibodies specific for viruses, bacteria, allergens and autoantigens have been detected. Serum polyclonal IgD concentrations are increased in various diseases, including the hyper IgD syndrome and allergic disorders, which raises the question of a possible role of IgD in such disorders. Conversely, some recent studies aimed at measuring IgD in patients with immunodeficiency or Henoch-Schonberg purpura reported undetectable serum IgD.Immunoglobulin D deficiency is a defect of humoral immunity that is characterized by abnormally low serum levels of IgD immunoglobulins. Little is known about the normal function of IgD, and few clinical signs or symptoms are associated with its absence. Individuals with low or absent levels of IgD do not appear unusually predisposed to infections.Family studies from one report indicate that low serum IgD levels may be inherited in an autosomal recessive fashion.Genetic rearrangements occur during the maturation of B lymphocytes, eventually resulting in the surface expression of both IgM (immunoglobulin M) and IgD on mature B cells. Cell signaling occurs through this surface IgD. IgD production by B cells is stimulated by interleukin-4 (IL-4) and interleukin-10 (IL-10).IgD deficiency is associated with the specific human leukocyte antigens HLA-B18, F1C30, and DR3 in a Spanish Basque population and HLA-B8, SC01, DR3 in white subjects in an American study.RESEARCH: Previous studies have indicated that IgD may play a role in B cell tolerance. To understand the role of IgD in B cell tolerance and autoimmunity, the researchers examined the development of autoimmune syndrome in lpr mice deficient for IgD. The present study showed that IgD deficiency did not alter lymphoproliferation and lymphocyte activation in lpr mice. The survival and proliferation of B cells were not affected by the absence of IgD, indicating that IgD BCR-mediated signals do not have an important role in negative selection of autoreactive B cell clones. Interestingly, compared to IgD-competent littermates, lpr mice with IgD deficiency had elevated autoantibody production, increased deposition of immune complex in the kidney and more severe nephritis. Accumulation of abnormal CD4(-), CD8(-), ??(+) T cells was accelerated in IgD(-/-) lpr mice compared to lpr mice. These results suggest that IgD BCR-mediated signals may be involved in the differentiation of autoreactive B cells into plasma cells and abnormal T cell expansion.Symptoms:No specific signs or symptoms are associated with isolated IgD deficiency; therefore, this condition is usually discovered incidentally during immunological laboratory testing.Diagnosis:Measure all classes of quantitative immunoglobulin levels IgA, IgG, IgM, and IgE. However, quantification of the IgG subclass is usually not necessary. Measuring these levels helps exclude a more extensive humoral immunodeficiency. Low levels of IgD may be associated with the presence of other immune disorders.Consider screening laboratory testing for complement disorders (eg, CH50), as well.Treatment:Isolated IgD deficiency does not require treatment. Specifically, intravenous or subcutaneous immunoglobulin replacement therapy is not indicated. Such immunoglobulin replacement should be considered only if an associated immunodeficiency (eg, common variable immunodeficiency) is present, which is normally treated with immunoglobulin replacement.Promptly treat any infections with appropriate antibiotics. Dosage, route, and duration of therapy depend on the suspected pathogen, specific drug chosen, and response to therapy. Check the monograph of a particular antibiotic for detailed information concerning contraindications, drug interactions, and precautions.NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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