The presence of clonal lymphoid cells, thought to be different from neoplastic plasma cells (PC), in patients with multiple myeloma (MM) has been suggested in the literature. In the current study we intended to use a new approach of determining cytoplasmic immunoglobulin (clg) expression by flow cytometry to evaluate the clonal lymphoid cells. Twenty-eight samples, 7 peripheral blood (PB), 21 bone marrow (BM), were obtained from 17 multiple myeloma (MM) patients and 11 patients for evaluation of other hématologie malignancies (used as controls). Samples were prepared by lysed-whole-blood technique and incubated with PE-coupled anti-CD38 and FITC-coupIed anti-CD45. The cells were fixed and acquired on a FACSCalibur flow cytometer (first acquisition). The cells were then permeabilized, incubated with either FITC-coupled anti-kappa or FITC-coupled antilambda and re-acquired (second acquisition). Analysis of the data was achieved by gating on the differing intensities of CD38. The two-step acquisition procedure was designed to visualize the cell population that showed an increase of FITC fluorescence intensity during the second acquisition as compared to the first acquisition. This increase is specifically due to the cytoplasmic expression of either the kappa or lambda. None of the control patients showed evidence of any clonal population either in BM or PB specimens. In BM specimens, 12 (92 %) of 13 MM patients at different stages of disease exhibited clonal PC (CD38 strong, CD45 dim) ranging from 0.1% to 44.8% of total events collected. Furthermore, 11 of these 12 patients had another minute clonal population (CD38 dim, CD45 variable) of cells, ranging from .06% to .8% of total events, with the same light chain restriction as the PC. In PB specimens, two of four MM patients showed both clonal PC and the minute clonal population. These two patients were MM patients in the stage of progressive disease. In contrast, two MM patients without minute clonal population in PB were in remission. Our results indicated the presence of a minute clonal population expressing dim CD38 and variable CD45 in MM patients by the newly developed method. Additionally, the preliminary results suggest that the absence of the minute clonal population in PB may correlate with clinical course. Further study is needed to study the clinical significance of the minute clonal population in MM.
|Original language||English (US)|
|Issue number||11 PART II|
|State||Published - Dec 1 2000|
ASJC Scopus subject areas
- Cell Biology