Cellular localization of the galactose-binding lectin from human serum

Area of Science:

• Immunology
• Biochemistry
• Cell Biology

Background:

• A human serum lectin, SL2, has been previously isolated and characterized.
• Understanding the cellular localization and binding specificities of SL2 is crucial for elucidating its biological functions.

Purpose of the Study:

• To determine the cellular localization of the SL2 lectin using specific polyclonal antibodies.
• To investigate the binding characteristics of SL2 to different immune cell types and specific cell surface molecules.

Main Methods:

• Cytofluorimetry was employed to assess antibody binding to various blood cells.
• Immune cell lines (Jurkat T cell lymphoma and IM-9 B cell line) were used to study SL2 interactions.
• Oligosaccharide binding assays were performed to identify high-affinity ligands for SL2.
• Cell lysis, electrophoresis, and Western blotting were utilized to identify the protein recognized by anti-SL2 antibodies.

Main Results:

• Anti-SL2 antibodies demonstrated specific binding to lymphocytes and monocytes, excluding other blood cell types.
• SL2 binding was observed on Jurkat T cells but not on IM-9 B cells.
• Jurkat T cells bound oligosaccharides with high affinity for SL2, including GalNAcalpha and Fucalpha1-2Gal.
• Anti-SL2 antibodies inhibited the interaction between Jurkat cells and these specific oligosaccharides.
• Western blotting identified a 14-kD protein on Jurkat cells recognized by anti-SL2 antibodies.

Conclusions:

• The SL2 lectin is specifically expressed on human lymphocytes and monocytes.
• SL2 interacts with a 14-kD protein on T cells, suggesting a potential role in T cell recognition or function.
• The identified binding specificities provide insights into the molecular interactions mediated by SL2 in the immune system.