Multiple ICAM-1 (CD54) epitopes are involved in homotypic B-cell adhesion

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Homotypic adhesion of human B cells is crucial for immune responses.
• Intercellular Adhesion Molecule 1 (ICAM-1, CD54) plays a role in cell-cell interactions.
• Understanding ICAM-1 epitopes involved in B cell adhesion is essential for therapeutic targeting.

Purpose of the Study:

• To characterize monoclonal antibodies (MoAbs) F10.2 and F10.3 that interfere with human B cell homotypic adhesion.
• To identify the specific epitopes on ICAM-1 recognized by these MoAbs.
• To elucidate the role of different ICAM-1 domains and glycosylation in B cell adhesion.

Main Methods:

• Precipitation studies to determine antibody targets.
• Binding assays using COS cells transfected with ICAM-1 cDNA.
• Inhibition assays with other MoAbs to map epitopes.
• Investigation of glycosylation effects on antibody binding.

Main Results:

• Both MoAbs F10.2 and F10.3 bind to ICAM-1.
• MoAb F10.2 recognizes an epitope on the first domain of ICAM-1.
• MoAb F10.3 recognizes a distinct epitope, potentially on domains 2, 3, or 4, influenced by glycosylation.
• The epitopes recognized by F10.3 and F10.2 (or LB-2) cooperate to mediate homotypic adhesion in ML1 B cells.

Conclusions:

• ICAM-1 homotypic B cell adhesion involves at least two distinct epitopes.
• One epitope is located on the first domain of ICAM-1.
• Another critical epitope's exposure is regulated by glycosylation, suggesting involvement of later domains.