Which immunoglobulin classes are typically found on the surface of circulating B lymphocytes?

The immunoglobulin classes typically found on the surface of circulating B lymphocytes are IgM and IgD. B lymphocytes, or B cells, express these two isotypes as part of their receptor complex when they are in their naive state, meaning they have not yet been activated or differentiated into plasma cells.

IgM serves as the primary antibody response during initial immune reactions and is important in B cell receptor signaling. It is the first immunoglobulin class produced during a primary immune response and is also the main antibody involved in complement activation. IgD, on the other hand, is present at lower levels and is thought to play a role in the activation and regulation of B cells, although its precise function is less well understood compared to IgM.

In contrast, other immunoglobulin classes such as IgG and IgE are typically not found on the surface of naive B cells. IgG is the main antibody for secondary immune responses and is secreted by plasma cells, while IgE is primarily involved in allergic reactions and response to parasitic infections. Similarly, IgA is mostly found in mucosal areas and secretions rather than on the surface of circulating B lymphocytes.

Thus, the presence of IgM and IgD on B lymphocytes