<immunology> This immunoglobulin (184 kD) is present at a low level (3-400 mcg/ml) but is a major immunoglobulin on the surface of B lymphocytes where it may play a role in antigen recognition. ... Its structure resembles that of immunoglobulin G but the heavy chains are of the delta type. ... (30 Mar 1998) ... 
Immunoglobulin D: Abbreviated IgD. A class of immunoglobulins found as antibodies on the surface of B cells (B lymphocytes). Almost nothing is known about the normal function of IgD.
[n] - one of the five major classes of immunoglobulins