Griffonia simplicifolia I isolectin as a functionally monovalent probe for use in flow cytometry

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Lectins' tendency to agglutinate cells limits their use in flow cytometry for detecting cell surface carbohydrates.
• Griffonia simplicifolia I-A3B (GS I-A3B) is a tetrameric isolectin with A and B subunits, both binding alpha-D-galactopyranosyl (alpha-D-galp) end groups.

Purpose of the Study:

• To develop a functionally monovalent, nonagglutinating lectin probe for flow cytometry.
• To enable accurate detection of cell surface alpha-D-Galp end groups using a modified GS I-A3B isolectin.

Main Methods:

• Utilizing a fluoresceinated tetrameric isolectin (FITC-GS I-A3B).
• Employing low concentrations of N-Acetyl-D-galactosamine (GalNAc) to selectively block high-affinity A subunits.
• Testing the probe on Ehrlich ascites tumor cells and rat alveolar macrophages.

Main Results:

• The addition of GalNAc created a functionally monovalent probe, preventing agglutination.
• Lectin binding was concentration-dependent and specific, as shown by inhibition with methyl alpha-D-galactopyranoside (Met alpha-D-Galp).
• Absence of GalNAc and Met alpha-D-Galp led to cell agglutination, confirming A subunit activity.

Conclusions:

• A modified FITC-GS I-A3B isolectin with GalNAc serves as an effective, nonagglutinating probe for flow cytometry.
• This method overcomes limitations of lectin use in cell surface carbohydrate detection.
• The approach allows for specific and sensitive analysis of alpha-D-Galp end groups on various cell types.