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Do myelomatous plasma cells really express surface immunoglobulins?
M Ocqueteau1, J F San Miguel, M González
1Becario DGICYT, Salamanca, Spain.
Haematologica
|September 1, 1996
Summary
Surface immunoglobulins (sIg) are traditionally absent in plasma cells (PC). This study confirms that some myeloma patients (35%) do express specific sIg, challenging previous assumptions in hematologic research.
Area of Science:
- Immunology
- Hematology
- Cell Biology
Background:
- Plasma cells (PC) are typically defined by the absence of surface immunoglobulins (sIg).
- Recent reports suggest sIg expression in a subset of myeloma patients, but findings remain inconsistent.
- Clarifying sIg expression in myeloma is crucial for understanding disease biology and potential therapeutic targets.
Purpose of the Study:
- To definitively assess the presence and specificity of surface immunoglobulin expression on myelomatous plasma cells.
- To differentiate true surface immunoglobulin staining from cytophilic or cytoplasmic immunoglobulin artifacts.
- To establish reliable methodology for detecting sIg on plasma cells in multiple myeloma.
Main Methods:
- Simultaneous immunofluorescence staining protocols were employed, including temperature control (37°C) and blocking assays.
- Blocking with non-conjugated anti-Ig light chains was used to exclude non-specific binding.
- Cytoplasmic staining was performed after cell membrane fixation and permeabilization.
- Triple staining for CD38, kappa, and lambda light chains quantified using MESF (molecule equivalents of soluble fluorochrome).
- B-cell chronic lymphocytic leukemia (B-CLL) cases and healthy donors served as controls.
Main Results:
- Surface immunoglobulin expression was detected in 7 out of 20 (35%) analyzed multiple myeloma patients.
- The observed surface staining was confirmed to be specific, ruling out artifacts.
- Methodology allowed for clear differentiation of surface versus cytoplasmic immunoglobulin staining.
Conclusions:
- This study provides robust evidence that a significant subset of multiple myeloma plasma cells can express specific surface immunoglobulins.
- The findings challenge the traditional definition of plasma cells and have implications for myeloma diagnostics and immunophenotyping.
- Validated methods can reliably detect specific sIg on myelomatous plasma cells, aiding further research.