Interactions between ricinus agglutinin and human IgM and IgG

Area of Science:

• Immunology
• Biochemistry
• Glycobiology

Background:

• Serum glycoproteins contain terminal nonreducing galactose residues.
• Immunoglobulins M (IgM) and G (IgG) are key serum glycoproteins.
• Ricinus agglutinin is a lectin known to bind galactose.

Purpose of the Study:

• To investigate the interaction of purified Ricinus agglutinin with serum glycoproteins, specifically IgM and IgG.
• To determine the binding specificity of Ricinus agglutinin to different immunoglobulin subclasses.

Main Methods:

• Quantitative precipitin tests were performed using Ricinus agglutinin and purified IgM and IgG.
• Affinity chromatography was employed using insolubilized Ricinus agglutinin.
• Monoclonal IgG1 and IgG3 proteins were isolated and tested for reactivity.

Main Results:

• Ricinus agglutinin effectively precipitated nearly 100% of IgM.
• Only about 10% of polyclonal IgG reacted with Ricinus agglutinin.
• Ricinus agglutinin specifically reacted with IgG3 monoclonal proteins, but not IgG1.

Conclusions:

• Ricinus agglutinin selectively precipitates serum glycoproteins containing terminal galactose residues.
• The lectin exhibits differential binding to immunoglobulin isotypes, with strong affinity for IgM and specific reactivity towards IgG3.