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Immunoglobulin light chain restriction and clonal rearrangement in nodular paragranuloma
1Department of Biomedical Sciences and Human Oncology, University of Turin, Italy.
Insights
B-cell clonality in nodular paragranuloma (NP) involves both lymphocytes and lympho-histiocytic (L&H) cells. Molecular analysis confirms a shared lambda light chain gene rearrangement, indicating a common clonal origin for these cell types in NP.
Area of Science:
- Hematology
- Immunology
- Oncology
Background:
- Nodular paragranuloma (NP) is a rare lymphoid proliferation.
- The cellular composition and clonal nature of NP remain incompletely understood.
Purpose of the Study:
- To investigate the B-cell clonality in a case of nodular paragranuloma.
- To determine the relationship between lympho-histiocytic (L&H) cells and surrounding lymphocytes in NP.
Main Methods:
- Immunoglobulin (Ig) surface analysis and Ig gene rearrangement studies.
- Immunohistochemistry for Ig light chain expression on frozen sections.
- Molecular analysis of Ig lambda and kappa chain genes using restriction enzymes.
Main Results:
- Demonstrated B-cell clonality with a predominance of Ig lambda-expressing cells in both lymphocytes and L&H cells.
- Identified monoclonal rearrangement of the lambda chain gene, with near-complete deletion of the kappa gene.
- Molecular findings indicated clonal proliferation involved both L&H cells and surrounding lymphocytes.
Conclusions:
- L&H cells and B lymphocytes in NP share a common origin.
- Both L&H cells and surrounding lymphocytes are involved in the clonal proliferation characteristic of NP.
Abstract:
B-cell clonality was demonstrated in a typical nodular paragranuloma case (NP) by both immunoglobulin (Ig) surface analysis and Ig genes rearrangement studies. On frozen sections, immunostaining for Ig light chain expression revealed a clear-cut predominance of Ig lambda-expressing cells, recognizable as both small lymphocytes and lympho-histiocytic (L&H) cells. Accordingly, molecular analysis of the Ig genes showed a monoclonal rearrangement of the lambda chain gene, although no specific pattern of heavy chain gene rearrangement could be detected by JH analysis. The C lambda rearranged band was identified with two different restriction enzymes, excluding the hypothesis of a genomic polymorphism. Furthermore, the C kappa gene was almost completely deleted, indicating that the developmental hierarchy of Ig genes rearrangement has been respected. The molecular pattern of the C lambda hybridizing band was consistent with monoallelic rearrangement of almost the entire DNA sample, indicating that clonal proliferation was not limited to L&H cells, but also involved surrounding lymphocytes. This finding is in keeping with the immunohistochemical evidence of a lambda light chain restriction on both L&H cells and small lymphocytes, pointing to a close relationship between these two cell types. Our results as a whole suggest that L&H cells and B lymphocytes share a common origin and may both be involved in clonal proliferation in NP.