OSMT (Ontario Society of Medical Technologists) Practice Exam

Which antibody is most likely to be found on a B cell?

1. IgA

2. IgD

3. IgE

4. IgG

The correct answer is: IgD

The presence of IgD as an antibody primarily associated with B cells is central to understanding B cell maturation and activation. IgD serves as a crucial receptor on the surface of immature B cells, playing a significant role in the initiation of B cell activation upon encountering antigens. When a B cell binds to an antigen through IgD, it triggers subsequent steps leading to B cell proliferation and differentiation into plasma cells and memory cells. While other immunoglobulin classes, such as IgA, IgE, and IgG, have important functions in the immune response, they typically arise after B cells have been activated and undergone class switching. IgA is generally found in mucosal areas and is important for mucosal immunity, IgE is associated with allergic responses and protection against parasitic infections, and IgG is the most abundant antibody in the blood and is crucial for opsonization and neutralization of pathogens. Thus, the role of IgD as the principal antibody present on naive B cells prior to activation underscores its significance in the context of B cell biology.