Functions of Immunoglobulin D (IgD)

• Functions primarily as an antigen receptor on B cells and is thought to be involved in regulating B cell function when an antigen is encountered
• Can participate in generating and maintaining B-cell memory and may either regulate maturation of B cells or extend the lifespan of mature B cells in the periphery
• May be able to bind to antigens featuring widely spaced epitopes because of its long hinge region 
• Enhances humoral immune responses and mucosal immunity 
• May play a crucial role in the transition from susceptibility to the induction of B-cell tolerance and subsequent responsiveness
• Can regulate immune responses by either enhancing the protective antibody response of IgG, IgM, or IgA isotypes, or by inhibiting viral replication
• May be involved in allergic reactions as cross-linking of IgD on basophils triggers the release of antimicrobial, proinflammatory, and immunoactivating mediators