Abstract
In healthy humans, 60–70% of the B lymphocytes produce kappa light chains, while the remaining cells produce lambda light chains. Malignant transformation and clonal expansion of B lymphocytes lead to an altered kappa : lambda expression ratio, which is an important diagnostic criteria of lymphomas. Here, we compared three methods for clonality determination of suspected B cell lymphomas. Tumor biopsies from 55 patients with B cell malignancies, 5 B-lymphoid tumor cell lines, and 20 biopsies from patients with lymphadenitis were analyzed by immunohistochemistry, flow cytometry, and reverse transcription quantitative real-time PCR. Clonality was determined by immunohistochemistry in 52/53 cases, flow cytometry in 30/39 cases, and reverse transcription quantitative real-time PCR in 33/55 cases. In conclusion, immunohistochemistry was superior to flow cytometry and reverse transcription quantitative real-time PCR for clonality identification. Flow cytometry and reverse transcription quantitative real-time PCR analysis has complementary values. In a considerable number of cases tumor cells produced both kappa and lambda light chain transcripts, but only one type of light chain peptide was produced.
Highlights
B lymphocytes produce immunoglobulins consisting of a heavy chain and either a kappa (IGKC) or a lambda (IGLC) light chain
The samples were analyzed by IHC, flow cytometry (FC), and reverse transcription quantitative real-time PCR (RT-qPCR) for expression of IGKC and IGLC light chains (Tables 1 and 2)
The divergent results may in part be explained by the fact that biopsies, besides the tumor cells, often contain considerable numbers of normal lymphocytes that could contribute to the RNA samples analyzed by RT-qPCR and the cell population studied by flow cytometry
Summary
B lymphocytes produce immunoglobulins consisting of a heavy chain and either a kappa (IGKC) or a lambda (IGLC) light chain. Each B lymphocyte decides early by the rearrangement of its immunoglobulin genes which light chain to produce [1]. The single cell origin of malignant clones results in exclusive expression of IGKC or IGLC light chains in the vast majority of all B cell malignancies B cell tumors that produce both kappa and lambda chains have been reported [4]. In the present study we have used the same RT-qPCR method together with IHC and FC to analyze a larger cohort of 39 nonHodgkin lymphomas, 16 chronic lymphatic leukemias, and 5 B cell derived tumor cell lines.
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