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IgM expressed by leukemic CD5(+) B cells binds mouse immunoglobulin light chain
K M Weston1, S G Tangye, R D Dunn
1Immunobiology Unit, Department of Cell and Molecular Biology University of Technology, Sydney, Westbourne Street, Gore Hill, 2065, NSW, Australia.
Journal of Molecular Recognition : JMR
|August 14, 2001
Summary
Human IgM on B-cell chronic lymphocytic leukemia (B-CLL) cells binds to mouse immunoglobulin (Ig) molecules. This interaction involves the light chain of mouse IgG and highlights the polyreactive nature of B-CLL surface Ig.
Area of Science:
- Immunology
- Molecular Biology
Background:
- Mouse immunoglobulin (Ig) molecules bind to CD5(+) B cells in B-cell chronic lymphocytic leukemia (B-CLL).
- This interaction involves surface IgM and suggests polyreactive binding by malignant B-CLL cells.
Purpose of the Study:
- Further characterize the interaction between human IgM and mouse Ig molecules.
- Identify the specific components involved in this binding phenomenon.
Main Methods:
- Enzyme immunoassay to detect binding of secreted human IgM to mouse Ig.
- Western blot analysis to identify the epitope on mouse Ig.
- Cloning and expression of mouse IgG1 light chain in E. coli.
Main Results:
- Both kappa and lambda mouse Ig light chain classes bound to B-CLL cells.
- Dissociation constant for mouse IgG1 (K121) with B-CLL cells was 3.6 x 10(-7) M.
- Secreted human IgM bound to intact mouse Ig, recognizing an epitope on the light chain.
- Recombinant mouse IgG1 light chain bound to CLL B cells.
Conclusions:
- Human IgM is the reactive ligand interacting with mouse Ig.
- The binding of polyreactive IgM to mouse IgG occurs via the IgG light chain.
- This interaction is conformationally dependent.