Usefulness of Bcl-2 Expression and the Expression of Cytoplasmic Immunoglobulin Light Chains in the Differentiation Between B-Cell Lymphoma and Reactive Lymphocytic Proliferations in FNA.

Flow cytometry is helpful in differentiating between B-cell lymphoma (BCL) and reactive lymphocytic proliferation (RLP) in FNA biopsies. However; the presence of inconclusive surface immunoglobulin light chains (sIg LC) poses a problem. We investigated the usefulness of additional tests; namely Bcl-2 expression and expression of cytoplasmic Ig LC (cIg LC), mainly on samples with inconclusive sIg LC. Both tests were performed on 232 FNA samples from lymph nodes. Bcl-2 alone was determined qualitatively and quantitatively on 315 samples. The quantitative test was correctly positive in 76% of cases and falsely negative in 24%. The correctly positive results of the qualitative test were 11% points lower. cIg LC correctly identified 65% of BCL with dual positive sIg LC; 36% of BCL with difficult to interpret sIg LC and only 7% of BCL with negative sIg LC. The best results in differentiating between BCL and RLP were obtained when all three tests were used together. In samples with inconclusive sIg LC and additional monoclonal or polyclonal populations the κ:λ ratios did not differentiate between RLP and BCL. We propose that in case of inconclusive sIg LC Bcl-2 test is used first. The addition of cIg LC test is sensible only in cases with dual positive and difficult to interpret sIg LC.

Surface IgM λ light chain is involved in the binding and infection of infectious bursal disease virus (IBDV) to DT40 cells.

Infectious bursal disease virus (IBDV) is an important immunosuppressive virus in chickens. Surface immunoglobulin M (sIgM)-bearing B lymphocytes act as the major targets of IBDV in the bursa of Fabricius, and sIgM may function as one of the membrane binding sites responsible for IBDV infection. Recently, using the virus overlay protein binding assay, the chicken λ light chain of sIgM was identified to specifically interact with IBDV in a virulence-independent manner in vitro. To further investigate sIgM λ light chain-mediated IBDV binding and infection in pre-B cells, the cell line DT40, which is susceptible to both pathogenic and attenuated IBDV, was used. Based on the RNA interference strategy, the DT40 cell line whose λ light chain of sIgM was stably knocked down, herein termed DT40LKD, was generated by the genomic integration of a specific small hairpin RNA and a green fluorescence protein co-expression construct. Flow cytometry analysis indicated that the binding of IBDV to DT40LKD cells was significantly reduced due to the loss of sIgM λ light chain. In particular, reduced viral replication was observed in IBDV-incubated DT40LKD cells, and no viral release into cell culture medium was detected by the IBDV rapid diagnostic strips. In addition, the rescue of sIgM λ light chain expression restored viral binding and replication in DT40LKD cells. These results show that sIgM λ light chain appears to be beneficial for IBDV attachment and infection, suggesting that sIgM acts as a binding site involved in IBDV infection.

Surface Light Chain Expression in Primary Mediastinal Large B-Cell Lymphomas by Multiparameter Flow Cytometry.

OBJECTIVES: Primary mediastinal large B-cell lymphoma (PMLBL) is an aggressive B-cell lymphoma typically localized to the mediastinum. To date, no study has undertaken a comprehensive analysis of this entity by multiparameter flow cytometry. METHODS: Cases of PMLBL with diagnostic flow cytometry were identified from pathology databases of Boston Children's Hospital, Brigham and Women's Hospital, and Stanford Hospital. RESULTS: Most of these patients with PMLBL were women with a median age of 30 years who had stage 1 disease that lacked bone marrow involvement. By flow cytometry, 50% of all PMLBLs showed restricted surface immunoglobulin expression. When comparing patients with PMLBL by the absence or presence of surface light chain immunoglobulins, no differences were seen in the morphologic appearance; expression of CD23, CD30, or CD10; age at presentation; or clinical stage (P > .5 for all). In addition, both groups showed similarly good survival outcomes and were alive at last follow-up (11/14 [79%]; P = .542). CONCLUSIONS: This multi-institutional study demonstrates that 50% of PMLBLs can present with clonal surface light chain expression and that PMLBL is more immunophenotypically diverse than previously described. Furthermore, our findings suggest that the absence or presence of surface light chains should not be used as criteria for diagnosis in this disease.

Hairy cell transformation of human peripheral blood lymphocytes by Coxiella burnetii

Hairy cell (HC) transformation of human peripheral blood lymphocytes (PBL) by Coxiella burnetii was studied to clarify the significance of persistency of C. burnetii in a hairy cell line (designated "TOL"). TOL cells which exhibited HC characteristics in hairy cell leukemia (HCL) were persistently infected with C. burnetii. Two strains of C. burnetii, our isolate from TOL cells and the original isolate in 1935, the Nine Mile strain from American Type Culture Collection (ATCC, U.S.A), were inoculated to PBL cultures. HC transformation not only by our isolates (87%) but also by Nine Mile strain (100%) was demonstrated in an average of 20 days. The original observation that Coxiella induced HC transformation in vitro was also confirmed in experiments with PBL exposed to C. burnetii in vivo. Spontaneous development of HC were observed in cultures of PBL only from coxiellemic cases (12/24) but not from C. burnetii negative cases (0/57). All HC cell lines (34) as determined by their morphology and cytochemical markers of HC in HCL remained infected with C. burnetii invariably.