IgD emerged soon after IgM at the time of inception of the adaptive immune system and it is evolutionary conserved. Since discovered in 1965, the specific functions of IgD have only recently begun to be elucidated. While membrane IgD (mIgD) is clearly accepted as B cell receptors, the function of secretory IgD (sIgD) has been hitherto neglected. However, more evidence shows that IgD is related to some immunological diseases, which indicates that IgD is also involved in the communication between mucosal and systemic immune compartments. Indeed, the treatment of IgD-related diseases is focused on symptomatic relief rather than radical cure due to the lacking of a detailed understanding of IgD. Therefore, as an advanced biotech company, Creative Biolabs pays more attention to this enigmatic immunoglobulin molecule based on our established and mature antibodies research platforms. Up to now, there are many kinds of IgD-related diseases such as hyper-IgD syndromes, autoimmune diseases, and multiple myeloma. We are glad to share our accumulated experience with IgD and related diseases with our clients all over the world.
Introduction of IgD
B cells mediate humoral immunity by producing IgM, IgD, IgG, IgA, and IgE. While the biology of other immunoglobulins has been extensively studied, the regulation and function of IgD have remained less well understood. However, the preservation of IgD throughout evolution implies that IgD exerts important functions that confer a specific survival advantage to the host. IgD is found in human serum and on the surface of B cells, which is divided into two classes referred as to sIgD and mIgD. As for the other Ig, mIgD and sIgD differ by the C-terminal part of the heavy chain, namely a hydrophilic tail for sIgD and the short extracellular, hydrophobic, and intracytoplasmic regions specific of mIg.
Fig.1 IgD production and regulation in the aerodigestive mucosa. (Chen, 2020)
Function of IgD
IgD is the major component of the mature B lymphocyte receptors and mature B cells undergo alternative mRNA splicing to express IgD and IgM receptors with identical antigenic specificity. However, IgD helps peripheral accumulation of physiologically autoreactive B cells through its functional unresponsiveness to self-antigens but prompt readiness against foreign antigens.
While the mIgD was generally recognized as B cell receptor, the relationship between sIgD and diseases is not clear. Recent research suggests that sIgD appears to enhance mucosal homeostasis and immune surveillance by activating myeloid effector cells such as basophils and mast cells with IgD antibodies reactive against mucosal antigens, including commensal and pathogenic microbes.
Fig.2 The mIgD regulates peripheral B cell immunity (left) and the sIgD enhances mucosal immune (right). (Gutzeit, 2018)
IgD and Diseases
Although the implications of IgD in humoral immunity are unrevealed, IgD-related diseases continue to harm human health. Due to the low level in serum, IgD is applied as a sensitive biomarker in these diseases. However, targeted and immunosuppressive treatment remains disappointing because of the lacking of explicit expression of the pathogenesis of IgD-related diseases.
As a kind of arcane immune disorder, IgD-related diseases attract more attention from therapeutic molecule development groups including Creative Biolabs. For more details of IgD and related diseases, please click fowling keywords or contact us directly.
References
- Chen, K.; et al. Rethinking mucosal antibody responses: IgM, IgG and IgD join IgA. Nature Reviews Immunology. 2020, 20(7), 427-441.
- Gutzeit, C.; et al. The enigmatic function of IgD: some answers at last. European journal of immunology. 2018, 48(7), 1101-1113.
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