Studies on Human IgD

Abstract

Abstract Physicochemical studies were undertaken on two human IgD (Δ:λ) myeloma proteins. Sedimentation equilibrium analyses using a photoelectric ultraviolet scanner showed that the apparent weight-average molecular weight of IgD is 200,000 ± 2000. On the basis of carbohydrate content, IgD is a high carbohydrate immunoglobulin, the ratio of the oligosaccharide moieties being quite distinct from other high carbohydrate immunoglobulins, IgA, IgM and IgE. One IgD molecule differs considerably from another with regard to several amino acid residues, e.g., asp, glu, ser, ile, gly, ala and val. The proline content of IgD was low in comparison with the other immunoglobulins. One IgD myeloma patient excreted λ-type Bence Jones protein which contained 12 oligosaccharide moieties. Fluorescence emission maxima of IgD occurred at 326 nm and 330 nm, the excitation wavelengths being 278 nm and 295 nm, respectively. Temperature-dependent fluorescence emission spectra showed an absence of a definite transition temperature in the case of IgD, whereas both IgA and IgM showed a definite transition temperature of 60°C.