Next-generation IgVH sequencing CLL-like monoclonal B-cell lymphocytosis reveals frequent oligoclonality and ongoing hypermutation

Chronic lymphocytic leukemia (CLL) develops from CLL-like monoclonal B-cell lymphocytosis (MBL) which represents a low-level asymptomatic expansion of cells that phenotypically resemble CLL. Although antigen selection plays a key role during CLL development, it is not known whether this occurs in early MBL or only during progression to CLL. Recent studies suggested that MBL sometimes displays oligoclonality, but these used techniques with limited sensitivity and specificity and were not conclusive. In this study, we combine cell sorting and next-generation sequencing of rearranged immunoglobulin heavy chain variable (IgVH) genes to thoroughly assess the VH repertoire and oligoclonality of purified MBL cells. Clonal functional rearrangements or clonotypes were identified in 29 of 30 sequenced cases, with 7 or 24% having two clonotypes with unrelated CDR3 sequences. In four of the seven cases with unrelated clonotypes, VH segments from the same family were used. In addition, 6 of 29 cases showed clear evidence of ongoing VH gene hypermutation with three of these being among the seven with unrelated clonotypes. This study conclusively shows that MBL cases often contain multiple B-cell clones, the first to report ongoing VH gene mutation in MBL, and that antigen selection appears to occur in early MBL.

Genomic analyses reveal recurrent mutations in epigenetic modifiers and the JAK-STAT pathway in Sézary syndrome

Sézary syndrome (SS) is an aggressive leukaemia of mature T cells with poor prognosis and limited options for targeted therapies. The comprehensive genetic alterations underlying the pathogenesis of SS are unknown. Here we integrate whole-genome sequencing (n=6), whole-exome sequencing (n=66) and array comparative genomic hybridization-based copy-number analysis (n=80) of primary SS samples. We identify previously unknown recurrent loss-of-function aberrations targeting members of the chromatin remodelling/histone modification and trithorax families, including ARID1A in which functional loss from nonsense and frameshift mutations and/or targeted deletions is observed in 40.3% of SS genomes. We also identify recurrent gain-of-function mutations targeting PLCG1 (9%) and JAK1, JAK3, STAT3 and STAT5B (JAK/STAT total ∼11%). Functional studies reveal sensitivity of JAK1-mutated primary SS cells to JAK inhibitor treatment. These results highlight the complex genomic landscape of SS and a role for inhibition of JAK/STAT pathways for the treatment of SS.

Sézary syndrome is a T cell malignancy that has been poorly characterized at the genome level. In this study, Kiel et al. perform whole-genome analyses and identify mutations in the JAK–STAT pathway and show that primary cells are sensitive to JAK inhibitors.

A limited plasma cell flow cytometry panel with reflex CD138 immunohistochemistry is an optimal workflow process for evaluating plasma cell neoplasms in bone marrow specimens

OBJECTIVES

To determine the optimal workflow combination of flow cytometry (FC) and immunohistochemistry tests for efficient and cost-effective evaluation of plasma cell (PC) neoplasms (PCNs) in bone marrow (BM) specimens.

METHODS

Various workflow combinations of immunohistochemistry and FC for 4,031 BM specimens worked up for PCNs were compared. Turnaround time (TAT), immunohistochemistry usage, technical charges, and addendum/amendment rates were compared between periods to determine the optimal workflow combination.

RESULTS

Five distinct workflow periods were identified, with varying combinations of full or limited FC panels for assessing PC clonality and CD138/κ/λ immunohistochemistry for PC quantification. Replacement of full FC with limited FC was associated with significant reductions in TAT and number of immunostains performed per case. Elimination of immunohistochemistry on cases determined to be polyclonal by FC also resulted in significant reductions in immunohistochemistry usage and significant cost savings.

CONCLUSIONS

Assessment of PC clonality using a limited FC panel followed by reflex CD138 immunohistochemistry on cases that are monoclonal by FC provides an optimal and cost-effective workflow for evaluating PCNs in BM samples.

A quantitative allele-specific PCR test for the BRAF V600E mutation using a single heterozygous control plasmid for quantitation: a model for qPCR testing without standard curves

We describe a novel method for mutant allele quantitation using allele-specific PCR. The method uses a heterozygous plasmid containing one wild-type and one mutant sequence as a calibrator that is run at a single concentration, with each quantitative allele-specific PCR run. PCR data from both calibrator alleles, together with predetermined PCR efficiencies, are used to quantitate the mutant allele burden in unknown specimens. We demonstrate the utility of this method by using it to calculate BRAF V600E allele frequencies in cases of hairy-cell leukemia and show that it generates data that are comparable to those obtained via allele quantitation using conventional standard curves over a wide range of allelic ratios. This method is not subject to errors that may be introduced in traditional standard curves as the result of variations in pippetting or errors in the calculation of the absolute copy numbers of standards. Furthermore, it simplifies the workflow in the clinical laboratory and would provide significant advantages for efforts to standardize clinical quantitative PCR testing.

Detection of Merkel cell polyomavirus in chronic lymphocytic leukemia T-cells

Chronic lymphocytic leukemia/small cell lymphoma (CLL/SLL) is the most common B-cell leukemia/lymphoma, effecting >15,000 patients/year. There has been a proposed limited antigenic etiology, at least in some cases, of CLL/SLL based upon immunoglobulin heavy chain stereotypy found across unrelated cases, suggesting viral source may provide such antigenic stimulation. With an established epidemiological link between CLL/SLL and Merkel cell carcinoma (MCC), there has been some interest in investigating a possible leukemogenic role of Merkel cell polyomavirus (MCPyV), which is found in 80% of MCC cases. Recent studies have shown that MCPyV is present in lymphocytes in a small percentage of CLL/SLL cases, but the specific tropism for lymphocytes has not been well-established. In this study, we used quantitative PCR to investigate the presence of MCPyV in fluorescence activated cell sorted purified B- and T-cells from 23 CLL/SLL cases. Three of 23 cases (13%) had detectable MCPyV in T-cells, and none of the cases had detectable MCPyV in B-cells. These findings suggest that MCPyV may have tropism for T-cells in addition to previously reported neoplastic B-cells.

Whole-genome sequencing identifies recurrent somatic NOTCH2 mutations in splenic marginal zone lymphoma

NOTCH2 mutations in splenic marginal zone lymphoma are associated with poor prognosis.

Splenic marginal zone lymphoma (SMZL), the most common primary lymphoma of spleen, is poorly understood at the genetic level. In this study, using whole-genome DNA sequencing (WGS) and confirmation by Sanger sequencing, we observed mutations identified in several genes not previously known to be recurrently altered in SMZL. In particular, we identified recurrent somatic gain-of-function mutations in NOTCH2, a gene encoding a protein required for marginal zone B cell development, in 25 of 99 (∼25%) cases of SMZL and in 1 of 19 (∼5%) cases of nonsplenic MZLs. These mutations clustered near the C-terminal proline/glutamate/serine/threonine (PEST)-rich domain, resulting in protein truncation or, rarely, were nonsynonymous substitutions affecting the extracellular heterodimerization domain (HD). NOTCH2 mutations were not present in other B cell lymphomas and leukemias, such as chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; n = 15), mantle cell lymphoma (MCL; n = 15), low-grade follicular lymphoma (FL; n = 44), hairy cell leukemia (HCL; n = 15), and reactive lymphoid hyperplasia (n = 14). NOTCH2 mutations were associated with adverse clinical outcomes (relapse, histological transformation, and/or death) among SMZL patients (P = 0.002). These results suggest that NOTCH2 mutations play a role in the pathogenesis and progression of SMZL and are associated with a poor prognosis.

Improved flow cytometric detection of ZAP-70 in chronic lymphocytic leukemia using experimentally optimized isotypic control antibodies

INTRODUCTION

Expression of ZAP-70 by chronic lymphocytic leukemia (CLL) is associated with more aggressive disease and can help differentiate CLL using mutated immunoglobulin heavy chain variable genes (VH) from cases expressing unmutated VH genes. However, flow cytometric detection of ZAP-70 in CLL shows considerable variability and may be of questionable significance because most laboratories cannot correlate their results to clinical outcome or VH mutational data.

METHODS

Seventy cases of CLL were evaluated for ZAP-70 using a previously optimized staining procedure and two different methods to eliminate nonspecific background staining. One method, not previously reported, used isotypic control antibodies, where the concentrations were adjusted/optimized so that normal B-cells stained negatively for ZAP-70. The other used ZAP-70 stained peripheral blood B-cells from normal donors. The percentages of ZAP-70 stained CLL cells above the two thresholds were compared.

RESULTS

Concentrations of isotypic control antibodies had to be increased from manufacture's recommendations to insure normal B-cells were ZAP-70 negative. ZAP-70 levels among the CLL cases formed a bimodal distribution using the optimized isotypic control threshold, with 30 having low values (0-32% positive) and 40 high values (60-99% positive). In contrast, a continuous distribution was obtained with the ZAP-70 stained B-cell threshold. VH mutational status strongly correlated with the optimized control values as 29/30 low ZAP-70 cases had mutated VH genes and 37/40 high ZAP-70 cases used unmutated VH genes.

CONCLUSIONS

Use of an optimized isotypic control threshold could increase the reliability of flow based ZAP-70 detection and correlates well with VH mutational status.

Clinical laboratory analysis of immunoglobulin heavy chain variable region genes for chronic lymphocytic leukemia prognosis

Chronic lymphocytic leukemia (CLL) is the most common leukemia affecting adults in the western world. The clinical course of CLL is highly variable: cases that express mutated immunoglobulin heavy chain variable regions (IgV(H)) typically have a more indolent clinical course compared with those with unmutated IgV(H). The use of the V(H)3-21 variable region has also been found to confer a poor prognosis, independent of mutation status. Here we describe an assay for the identification of the expressed V(H) segment and its mutation status in CLL. This test uses whole blood-derived RNA and PCR primers annealing to the leader regions and the joining region segments. This approach allows more accurate determination of the IgV(H) mutation status relative to using framework region specific V(H) primers. An additional primer specific for the leader region of the V(H)3-21 segment is described and is shown to be necessary to identify this diagnostically important variable region. We successfully analyzed 99 of 103 samples, including five expressing the V(H)3-21 variable region. Approximately 5% of cases had complement determining region 3 sequences similar to previously reported cases, and overrepresentation of the V(H)1-69 segment was observed among unmutated cases. These results confirm the proper functioning and high success rate of this valuable prognostic for CLL designed for the use in a clinical laboratory setting.

Immunomagnetic bead separation of mononuclear cells from contaminating granulocytes in cryopreserved blood samples

Density gradient centrifugation usually allows efficient separation of mononuclear cells from granulocytes using fresh human blood samples. However, we have found that with cryopreserved blood samples, density gradient centrifugation fails to separate granulocytes from mononuclear cells and have explored using immunomagnetic anti-CD15 microbeads as an alternate method to separate these cell populations. Using cryopreserved blood samples from 10 healthy donors we have shown that granulocytes express a significantly higher level of CD15 antigen than monocytes and lymphocytes, which allows for their efficient separation from mononuclear cells using anti-CD15 microbeads. This procedure is critical for purification of individual cell populations from cryopreserved leukocyte samples and could also potentially be applied to avoid granulocyte contamination of mononuclear cells isolated from stored blood and from patients with sepsis or thermal injury.

Flow cytometric detection and serotyping of enterovirus for the clinical laboratory

Culture and serotyping of human enteroviruses by fluorescence microscopy are time-consuming and labor-intensive. Flow cytometry has the potential of being more rapid, sensitive, and objective but has not been used for these purposes in a clinical laboratory. Primary rhesus monkey kidney (PMK) cells were inoculated with several enterovirus serotypes and stained with enterovirus-specific antibodies for flow cytometry and indirect fluorescence antibody testing (IFA). Kinetic studies of coxsackievirus B1 and echovirus 30 infection of PMK cells were performed on days 1–4 after inoculation. Flow cytometry results for echovirus 6, 9, 11, and 30 and coxsackievirus B1 correlated with IFA in all cases. Coxsackievirus B1 and echovirus 30 infections were detected 1 day earlier by flow cytometry than IFA. Flow cytometry can be effectively used for detecting enterovirus-infected cells in a clinical laboratory with the advantages of better quantitation of low levels of infection and earlier detection of virally infected cells in culture systems.

Array CGH analysis of chronic lymphocytic leukemia reveals frequent cryptic monoallelic and biallelic deletions of chromosome 22q11 that include the PRAME gene

We used BAC array-based CGH to detect genomic imbalances in 187 CLL cases. Submicroscopic deletions of chromosome 22q11 were observed in 28 cases (15%), and the frequency of these deletions was second only to loss of the 13q14 region, the most common genomic aberration in CLL. Oligonucleotide-based array CGH analysis showed that the 22q11 deletions ranged in size from 0.34 Mb up to approximately 1 Mb. The minimally deleted region included the ZNF280A, ZNF280B, GGTLC2, and PRAME genes. Quantitative real-time PCR revealed that ZNF280A, ZNF280B, and PRAME mRNA expression was significantly lower in the 22q11 deletion cases compared to non-deleted cases.

Use of similar immunoglobulin VH gene segments by MALT lymphomas of the ocular adnexa

Extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue type (MALT lymphomas) develop from acquired reactive infiltrates directed against external or autoantigens. Although some European cases of ocular adnexal MALT lymphoma have been associated with Chlamydia psittaci infections, C. psittaci has not been detected in large studies of US-based cases. To evaluate whether the growth of US-based ocular adnexal MALT lymphomas may be promoted by a similar antigen, we identified and analyzed the expressed immunoglobulin VH genes in 10 cases. Interestingly, the VH genes in two cases used the same VH1 family V1-2 gene segment, and three cases used the same VH4 family V4-34 gene segment. The other five cases all used different gene segments V4-31, V5-51, V3-23, V3-30, and V3-7. All of the VH genes were mutated from germ line, with percent homologies ranging between 96.9 and 89.0%. The distribution of replacement and silent mutations within the VH genes was nonrandom consistent with the maintenance of immunoglobulin function and also strongly suggestive of antigen selection in the six VH genes with highest mutation loads. The CDR3 sequences in two of three VH-34 cases were the same size (15 amino acids) and had similar sizes in the two VH1-2 cases (18 and 16 amino acids). In conclusion, US-based MALT lymphomas of the ocular adnexa preferentially express a limited set of VH gene segments not frequently used by other MALT lymphomas and consistent with some recognizing similar antigens. Analysis of somatic mutations present within the VH genes is also consistent with antigen binding stimulating the growth of these lymphomas.

Small B-cell neoplasms with typical mantle cell lymphoma immunophenotypes often include chronic lymphocytic leukemias

Mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) are CD5+ small B-cell neoplasms (SBCNs) with overlapping features. Flow cytometric immunophenotyping is often used to help differentiate CLL from MCL, and a characteristic CLL phenotype is considered essentially diagnostic. However, previous studies have not specifically examined how well a typical MCL immunophenotype distinguishes MCL from CLL. We identified 28 cases of SBCN with typical flow cytometry-determined MCL immunophenotypes consisting mostly of peripheral blood and bone marrow specimens. Fluorescence in situ hybridization analysis indicated that 57% (16/28) had t(11;14) translocations consistent with MCL, while 32% (9/28) lacked t(11;14) translocations but harbored other cytogenetic abnormalities commonly found in CLL. There were no significant morphologic or immunophenotypic differences between the t(11;14)-positive and t(11;14)-negative cases. Our findings suggest that many blood-based SBCNs with typical MCL immunophenotypes likely represent cases of phenotypically atypical CLL, which would have important clinical implications.

Expression of T-plastin, FoxP3 and other tumor-associated markers by leukemic T-cells of cutaneous T-cell lymphoma

Peripheral blood cells from 28 patients with leukemic cutaneous T-cell lymphoma including 25 patients with Sezary syndrome were evaluated for expression of regulatory T-cell-associated markers (FoxP3, CD25, CTLA-4, neurophilin-1), T-cell activation markers (CD28 and its ligands B7.1 and B7.2) and NK cell-associated markers (NKG2D and its ligands Mic-A and Mic-B) using real-time quantitative polymerase chain reaction. T-plastin served as a positive genetic marker, and its expression correlated to blood tumor burden. More than 90% of samples had transcripts for CD28 and Mic-B, but less than 30% of samples expressed FoxP3, CTLA-4 and CD25. Expression of Mic-B by neoplastic cells could provide another mechanism to inhibit anti-tumor immune responses. FoxP3 expression correlated with a poor prognosis. Although the underlying mechanisms accounting for this correlation remain unclear, the expression of the Foxp3 and CTLA-4 regulatory elements indicates that a subset of leukemic cases displays a regulatory T-cell phenotype.

Fatal non-transplant-related epstein-barr virus-associated atypical lymphoid proliferations in infants and children: a clinicopathologic study

Most Epstein-Barr virus (EBV)-related infections in infants and children are asymptomatic or self-limited mild viral illnesses, but rare cases of a rapidly fatal disorder have been described. Failure of the cellular response to control EBV-related lymphoid proliferation leads to severe disease with multiple complications, including a fatal outcome or development of an EBV-driven, clonal lymphoid neoplasm. In this report we characterize 3 cases of fatal, nontransplant, or immunodeficiency-related EBV infection in very young children with immunophenotypic and molecular evidence of B/natural killer (NK)-T cell clonal expansion. An immunohistochemical staining panel included testing for B-cell antigen (CD20), and T/NK cell antigens including CD2, CD3, CD4, CD8, CD56, CD57, and TIA-1. T-cell and B-cell PCR clonality testing was performed on paraffin tissue specimens to identify clonal populations. The ages of these 3 patients ranged from 22 months to 4 years. Initial clinical presentations included pneumonia, abnormal liver function tests and fever, and lymphadenopathy. The 3 patients died within 17 to 72 days of presentation, and autopsy was performed on 1 patient. All cases demonstrated prominent atypical lymphoid or lymphohistiocytic infiltrates, and necrosis was present in 2 of the 3 cases. The atypical lymphocytes were positive for CD3 (cytoplasmic), CD2, CD8, TIA-1, and CD57 and negative for CD4. We molecularly identified B-cell clones in the 2 tested patients, who also showed evidence of hemophagocytosis. Fatal EBV infection is characterized by a morphologic spectrum with atypical lymphoid infiltrates and variable necrosis. Our molecular studies of these patients suggest a clonally-derived expansive process, most likely driven by EBV infection. Our results also suggest that development of clonality is associated with an aggressive clinical course and may be useful in predicting greater risk for fatal outcome. A high index of suspicion, coupled with appropriate serologic and molecular testing, aids in early recognition and diagnosis of these lymphoproliferative processes.

Whole-genome scanning by array comparative genomic hybridization as a clinical tool for risk assessment in chronic lymphocytic leukemia

Array-based comparative genomic hybridization (array CGH) provides a powerful method for simultaneous genome-wide scanning and prognostic marker assessment in chronic lymphocytic leukemia (CLL). In the current study, commercially available bacterial artificial chromosome and oligonucleotide array CGH platforms were used to identify chromosomal alterations of prognostic significance in 174 CLL cases. Tumor genomes were initially analyzed by bacterial artificial chromosome array CGH followed by confirmation and breakpoint mapping using oligonucleotide arrays. Genomic changes involving loci currently interrogated by fluorescence in situ hybridization (FISH) panels were detected in 155 cases (89%) at expected frequencies: 13q14 loss (47%), trisomy 12 (13%), 11q loss (11%), 6q loss (7.5%), and 17p loss (4.6%). Genomic instability was the second most commonly identified alteration of prognostic significance with three or more alterations involving loci not interrogated by FISH panels identified in 37 CLL cases (21%). A subset of 48 CLL cases analyzed by six-probe FISH panels (288 total hybridizations) was concordant with array CGH results for 275 hybridizations (95.5%); 13 hybridizations (4.5%) were discordant because of clonal populations that comprised less than 30% of the sample. Array CGH is a powerful, cost-effective tool for genome-wide risk assessment in the clinical evaluation of CLL.

CD158k/KIR3DL2 is a useful marker for identifying neoplastic T-cells in Sézary syndrome by flow cytometry

Enumeration of neoplastic T-cells in peripheral blood specimens is necessary for the diagnosis of Sézary syndrome (SS) and monitoring treatment responses. Because neoplastic T-cells in SS can be difficult to identify by morphology alone, flow cytometry immunophenotyping is often utilized. However, the reported immunophenotypic criteria for identifying neoplastic T-cells in SS are variable, not present in all cases, or sometimes found in reactive T-cell populations. Peripheral blood lymphocytes from 33 cases of SS were evaluated for the expression of pan-T cell antigens and killer cell immunoglobulin-like MHC receptors (KIR) CD158a, CD158b, CD158e, CD158i, and CD158k by multiparameter flow cytometry using monoclonal antibodies EB6, GL183, FES172, Z27, and Q66. A variety of abnormalities related to expression of pan-T-cell antigens typical of neoplastic T-cells were observed. Expression of CD158k was observed in 32/33 cases and restricted to the phenotypically abnormal T-cell populations, while expression of other KIR was mostly negative. Our findings confirm and extend recent reports by one group that CD158k is expressed by most SS cases. Moreover, our observation that CD4 positive, CD7 negative T-cells are mostly CD158k negative further suggests that CD158k may be able to help identify and enumerate neoplastic T-cells in SS even when present at low levels.

Optimization of flow cytometric measurement of ZAP-70 in chronic lymphocytic leukemia

BACKGROUND

The goal of this study was to optimize a cell staining procedure for flow cytometric detection of zeta-chain associated protein-70 (ZAP-70). Our specific objectives were to improve antibody selection criteria, identify a cell permeabilization procedure better tailored to ZAP-70 analysis, as well as to establish objective criteria to control antigen stability.

METHODS

Sequentially titrated 2F3.2-FITC, 1E7.2-FITC, and 1E7.2-Alexa Fluor 488 anti-ZAP-70 antibodies were used to stain normal B and T cells and Scatchard analysis was applied to calculate K(d) and B(max) values from saturation curves of specific binding. ZAP-70 staining was compared in cells permeabilized with two commercially available kits, Triton X-100, and a custom saponin procedure.

RESULTS

Normal B-cells were found to provide an excellent measure of nonspecific staining while varying ZAP-70 antibodies and concentrations. Comparing Scatchard analyses of specific T-cell binding revealed that 1E7.2-Alexa Fluor 488 had the highest binding affinity of the tested anti-ZAP-70 antibodies and was the best choice. The highest levels of ZAP-70 fluorescence occurred when cells were permeabilized using a noncommercial saponin procedure. Decrease of chronic lymphocytic leukemia cell viability correlated with diminished ZAP-70 expression; when viability was lower than 95% the percentage of bright positive samples was significantly decreased, indicating a possibility of false-negative results.

CONCLUSIONS

The efficiency and reliability of flow cytometric detection of ZAP-70 can be optimized by using Scatchard analysis to help select the most effective antibodies and antibody concentrations that maximize specific to nonspecific binding, by using a "custom" ZAP-70 permeabilization procedure, and by better controlling antigen stability by measuring cell viability.

A new DNA-based test for detection of nucleophosmin exon 12 mutations by capillary electrophoresis

Mutations in nucleophosmin (NPM1) exon 12 are thought to be the most common genetic event in acute myelogenous leukemia (AML) and to confer favorable clinical prognoses. In this report, we describe a simple molecular test for the detection of NPM1 exon 12 mutations in patients with AML using polymerase chain reaction amplification of genomic DNA followed by the analysis of amplification products by capillary electrophoresis. Mutations were reproducibly detected when present in at least 5% of cells, and all NPM1 exon 12 mutations reported to date in AML could be identified using this method. This method was successfully employed using paraffin-extracted DNA, allowing for the examination of archived clinical specimens, and the assay was validated by the direct sequencing of 33 patient samples. This sensitive test is straightforward to perform and provides important information that can influence both the clinical management and treatment options for many patients with AML.

Quantitation of Plasma Cells in Bone Marrow Aspirates by Flow Cytometric Analysis Compared With Morphologic Assessment

Context.—Accurate quantitation of bone marrow plasma cells is an important component in the diagnosis and posttreatment assessment of plasma cell dyscrasias. Although flow cytometry is sometimes used for this purpose and can rapidly evaluate many cells, the accuracy of flow-based plasma cell quantitation compared with morphologic assessment (currently the gold standard) is uncertain as direct comparison studies have not been previously reported.

Objective.—To determine how percentages of plasma cells in diagnostic aspirate smears quantitated by morphologic assessment relate to percentages of plasma cells quantified by flow cytometry.

Design.—Thirty bone marrow cases with 10% or more plasma cells and leukemia/lymphoma flow cytometry immunophenotyping studies were identified from our hematopathology database. The Wright-stained aspirate smears, marrow biopsy sections, and flow cytometry histograms were reviewed.

Results.—Morphologically determined plasma cell percentages from the diagnostic aspirate smears were consistently higher than those determined by flow cytometry. Much of this difference appeared to be related to differences in sample quality. However, the cellular processing involved in performing flow cytometry also appeared to reduce plasma cell percentages in many cases.

Conclusions.—This study helps define the limitations of flow cytometry for quantitating plasma cell loads in marrow aspirate specimens that may significantly affect the diagnosis or assessment of treatment response.

Analysis of immunoglobulin V genes suggests cutaneous marginal zone B-cell lymphomas recognise similar antigens

Extranodal marginal zone B-cell lymphomas (EMZL) are thought to develop from reactive infiltrates that represent immune responses to external or auto-antigens. Except for gastric EMZL, the antigenic triggers of EMZL development are mostly unknown, although a subset of cutaneous EMZL have been associated with Borrelia burgdorferi infections. To further evaluate whether a common antigen may be promoting the development of cutaneous EMZL, the immunoglobulin heavy chain variable (V(H)) genes from eight USA cases were sequenced and analysed. All used V(H)3 family gene segments, with 2/8 using the same V3-30 segment, 2/8 using the closely related V3-30.3 or V3-33 segments, 6/8 containing mutations and 2/7 showing evidence of ongoing mutation. Many of the complimentarity-determining region 3s (CDR3s) also showed similarities in length and displayed conserved amino acid motifs in the non-templated areas between the diversity and joining segments. The use of similar V(H) gene segments and conserved CDR3 amino acid motifs suggests that some of these cutaneous EMZL may bind the same or similar antigen via their surface immunoglobulin receptor. Analysis of the somatic mutations present in many of the V(H) genes was also consistent with antigen directly stimulating the growth of cutaneous EMZL.

Flow cytometric analysis of different CD14 epitopes can help identify immature monocytic populations

Accurate diagnosis of monocytic neoplasms often is dependent on quantitating monoblasts, promonocytes, and monocytes. However, distinguishing these populations by morphologic assessment alone can be difficult and subject to significant intraobserver variability. We evaluated a 4-color flow cytometry technique using different anti-CD14 antibodies that recognize the MO2 and MY4 epitopes to identify monoblasts, promonocytes, and monocytes. Normal control specimens and 18 cases of monocytic neoplasia were evaluated and results correlated with morphologic findings. We found the MY4 epitope first appearing at the early promonocyte stage and the MO2 epitope appearing only on mature monocytes after the promonocyte stage. Expression of the MY4 and MO2 epitopes by neoplastic monocyte populations was found to usually parallel the normal monocyte differentiation patterns, although exceptions were noted. Our study suggests that 4-color flow cytometry may be an especially useful adjunct for morphologically difficult cases by providing an immunophenotypic measure of neoplastic monoblasts and promonocytes.

T-cell large granular lymphocyte leukemias have multiple phenotypic abnormalities involving pan-T-cell antigens and receptors for MHC molecules

T-cell large granular lymphocyte (T-LGL) leukemias represent monoclonal T-cell expansions that express CD16, CD56, or CD57 and cause cytopenias. The identification of T-LGL leukemias can be difficult because reactive T-LGL cells also can express CD16, CD56, and CD57, and many leukemia cases show only mild lymphocytoses. In this study, 23 T-LGL leukemia cases were analyzed by 3- and 4-color flow cytometry to identify markers that could aid in discriminating leukemic from normal T-LGL. In most cases (18/23), abnormalities (bright, dim, or negative expression) of 2 or more pan-T-cell antigens were identified, with all cases showing abnormal CD5 levels. Abnormal expression of CD94 was identified in 22 of 23 cases, and 15 of 21 cases also showed abnormal expression of class 1 MHC receptor molecules identified by antibodies against CD158a, CD158b, CD158e, CD158i, CD158k, and CD94. These studies help define abnormal phenotypic features typical of T-LGL leukemia that may have important diagnostic value.

Hairy cell leukemia variant: fact or fiction

Hairy cell leukemia variant (HCL-V) is a poorly described, rare B-cell lymphoproliferative disorder typically positive for CD103 and CD11c, while lacking CD25. Splenic marginal zone lymphomas (SMZL) also have this unusual phenotype in 15% to 25% of cases, have other overlapping clinical or morphologic features, and are more common than HCL-V. The purpose of our study was to better characterize HCL-V and determine whether most cases could be distinguished from SMZL. Cases with an HCL-V phenotype were identified from our flow cytometry service, and 10 were selected for further study based on bone marrow or splenic tissue availability. All cases had cytologic features consistent with HCL-V, and 9 of 10 patients had lymphocytosis. Bone marrow involvement was mostly interstitial and/or sinusoidal without lymphoid nodules. Coexpression of preswitched with postswitched heavy chain isotypes, an unusual feature of HCL, was seen in 2 of 4 cases. This study better defines HCL-V and establishes that most cases do not represent SMZL.

Flow cytometric analysis of BCL-2 can distinguish small numbers of acute lymphoblastic leukaemia cells from B-cell precursors

Flow cytometric identification of small numbers of precursor B-cell acute lymphoblastic leukaemia (B-ALL) cells in post-treatment marrow specimens could benefit from the identification of additional, easily detectable markers that could be used in most cases. In this study, we evaluate whether bcl-2 expression quantified by four-colour flow cytometry can be effectively used to discriminate precursor B-ALL blasts from normal B-cell precursors (haematogones) and function as a leukaemia-specific marker. Levels of bcl-2 in the 22 precursor B-ALL cases studied were found to be significantly higher (over sixfold higher on average) than those present in haematogone populations from 22 control marrow specimens. Higher relative levels of bcl-2 expression in the B-ALL cases were maintained with respect to both immature CD34+ and more mature CD34- haematogone subsets, and appeared stable. Dilutional studies indicated that multiparameter flow cytometry analysis using bcl-2 could identify precursor B-ALL blasts representing as few as 1% of CD19+ cells or 0.01% of total leucocytes in bone marrow specimens containing substantial numbers of haematogones. This study suggests that bcl-2 may be an important marker for flow cytometric detection and quantification of small numbers of residual precursor B-ALL cells in bone marrow specimens.

Indolent mantle cell lymphoma with nodal involvement and mutated immunoglobulin heavy chain genes

Mantle cell lymphoma (MCL) is typically considered an aggressive but incurable neoplasm composed of cyclin D1+ monoclonal B-cells with a t(11;14)(q13;q32) and usually unmutated immunoglobulin (Ig) genes. Although it has been suggested that a more indolent leukemic disorder exists with the same phenotype and genotype but with mutated Ig genes, others have considered these cases to be variants of chronic lymphocytic leukemia. We present a case of an indolent MCL that was documented with cyclin D1 expression in a lymph node biopsy performed more than 12 years ago. The patient has peripheral blood involvement with a lymphocyte count in the reference range, variable thrombocytopenia, and minimal adenopathy but is otherwise well, never having received any antineoplastic therapy. Study of peripheral blood samples from 2002 revealed a CD5-variable B-cell monoclonal proliferation with a t(11;14)(q13;q32) plus other karyotypic abnormalities, positive fluorescence in situ hybridization studies for the CCND1/IgH translocation, and clonal Ig gene rearrangement with mutated Ig genes (95.7% homology to VH 4-31). The subtle but diagnostic lymph node biopsy in this case helps to further support that an indolent t(11;14) monoclonal lymphocytosis with mutated Ig genes can represent an MCL variant rather than chronic lymphocytic leukemia.

Analysis of CD10+ hairy cell leukemia

Hairy cell leukemia (HCL) has been reported to sometimes express CD10. However, the reported frequencies have been quite variable and the significance of CD10 expression has not been addressed. Cases of HCL submitted to our flow cytometry service during a 2-year period were evaluated for CD10 expression. Information regarding demographics, clinical manifestations, tissue morphologic features, and response to treatment was reviewed. Of the 97 HCL cases identified, 10 expressed CD10. The level of CD10 staining was typically well above control levels and also could be detected easily by immunohistochemical analysis. All cases analyzed were negative for bcl-6. Our study suggests that approximately 10% of otherwise typical cases of HCL show aberrant CD10 expression. CD10+ HCL cases seem to be morphologically and clinically similar to CD10-HCL cases. Appreciating that HCL can express CD10 may be especially important when evaluating specimens with suboptimal morphologic features and/or limited immunophenotyping panels.

Importance of CD117 in the evaluation of acute leukemias by flow cytometry

BACKGROUND

The issue of which specific antibodies need to be used when evaluating acute leukemias by flow cytometry is controversial.

METHODS

Recent studies have suggested that antibodies against CD117 or c-kit are not essential for the assignment of blast lineage by flow cytometry, even though CD117 appears to be a very specific marker for myeloid lineage acute leukemias. We report a case of acute myeloid leukemia M2 subtype with an 8:21 translocation, where the leukemic blasts expressed CD117, CD19, and CD15 but did not show definitive expression of the myeloid markers CD13 or CD33.

RESULTS AND CONCLUSIONS

This study highlights the importance of CD117 when evaluating acute leukemias by flow cytometry, which was necessary in this case to suggest that the blasts were phenotypically abnormal myeloblasts. In addition, this case presented an unusual acute myeloid leukemia phenotype that will likely be encountered by others and could be difficult to interpret.

Splenic marginal zone lymphomas appear to originate from different B cell types

Splenic marginal zone lymphomas (SMZLs) have been proposed to originate from postgerminal center memory B cells that usually have mutated immunoglobulin heavy-chain variable (VH) genes. However, the majority of SMZLs are thought to express both IgD and IgM, which is more typical of naïve B cells that have unmutated VH genes. To better define the SMZL cell of origin and pathogenesis, we studied the histological and immunophenotypic features of eight cases and also sequenced their rearranged VH genes. Half of the cases had unmutated VH genes consistent with a naïve B-cell origin and half had mutated VH genes consistent with a memory B-cell origin. Most of the unmutated cases (three of four) were positive for IgD, which further supports a naïve B-cell origin, whereas the others were negative. In addition, VH gene segment use seems to be nonrandom because seven of eight cases used genes from the VH1 or VH4 families and repetitive use of the V1-2, V1-69, and V4-34 gene segments was observed. Our results suggest there are two types of SMZLs, one that originates from naïve marginal zone B cells in addition to one that originates from memory marginal zone B cells, and that antigen selection may be occurring during lymphomagenesis.

Salivary gland mucosa-associated lymphoid tissue lymphoma immunoglobulin V(H) genes show frequent use of V1-69 with distinctive CDR3 features

Salivary gland mucosa associated lymphoid tissue (MALT) type lymphomas are B-cell neoplasms that develop out of a reactive infiltrate, often associated with Sjögren's syndrome. Previous reports from our laboratory involving 10 patients suggested these lymphomas expressed a restricted immunoglobulin (Ig) V(H) gene repertoire with over use of V1-69 gene segments. To better determine the frequency of V1-69 use and whether there may also be selection for CDR3 structures, we sequenced the V(H) genes from 15 additional cases. Over half of the potentially functional V(H) genes (8 of 14) used a V(H)1 family V1-69 gene segment, whereas the other cases used different gene segments from the V(H)1 (V1-46), V(H)3 (V3-7, V3-11, V3-30.3, V3-30.5), and V(H)4 (V4-39) families. The 8 V1-69 V(H) genes used 5 different D segments in various reading frames, but all used a J4 joining segment. The V1-69 CDR3s showed remarkable similarities in lengths (12-14 amino acids) and stretches of 2 to 3 amino acids between the V-D and D-J junctions. They did not resemble CDR3s typical of V1-69 chronic lymphocytic leukemias. This study extends our earlier work in establishing that salivary gland MALT lymphomas represent a highly selected B-cell population. Frequent use of V1-69 appears to differ from MALT lymphomas that develop at other sites. The high degree of CDR3 similarity among the V1-69 cases suggests that different salivary gland lymphomas may bind similar, if not identical epitopes. Although the antigen specificities are presently unknown, similar characteristic CDR3 sequences are often seen with V1-69 encoded antibodies that have anti-IgG or rheumatoid factor activity. (Blood. 2000;95:3878-3884)

Epstein-Barr virus-negative post-transplant lymphoproliferative disorders: a distinct entity?

Post-transplant lymphoproliferative disorders (PTLDs) are usually but not invariably associated with Epstein-Barr virus (EBV). The reported incidence, however, of EBV-negative PTLDs varies widely, and it is uncertain whether they should be considered analogous to EBV-positive PTLDs and whether they have any distinctive features. Therefore, the EBV status of 133 PTLDs from 80 patients was determined using EBV-encoded small ribonucleic acid (EBER) in situ hybridization stains with or without Southern blot EBV terminal repeat analysis. The morphologic, immunophenotypic, genotypic, and clinical features of the EBV-negative PTLDs were reviewed, and selected features were compared with EBV-positive cases. Twenty-one percent of patients had at least one EBV-negative PTLD (14% of biopsies). The initial EBV-negative PTLDs occurred a median of 50 months post-transplantation compared with 10 months for EBV-positive cases. Although only 2% of PTLDs from before 1991 were EBV negative, 23% of subsequent PTLDs were EBV negative (p <0.001). Of the EBV-negative PTLDs, 67% were of monomorphic type (M-PTLD) compared with 42% of EBV-positive cases (p <0.05). The other EBV-negative PTLDs were of infectious mononucleosis-like, plasma cell-rich (n = 2), small B-cell lymphoid neoplasm, large granular lymphocyte disorder (n = 4) and polymorphic (P) types. B-cell clonality was established in 14 specimens and T-cell clonality was established in three (two patients). None of the remaining specimens were studied with Southern blot analysis and some had no ancillary studies. Rearrangement of c-MYC was identified in two M-PTLDs with small noncleaved-like features, and rearrangement of BCL-2 was found in one large noncleaved-like M-PTLD. Ten patients were alive at 3 to 63 months (only three patients received chemotherapy). Seven patients, all with M-PTLDs, are dead at 0.3 to 6 months. Therefore, EBV-negative PTLDs have distinct features, but some do respond to decreased immunosuppression, similar to EBV-positive cases, suggesting that EBV positivity should not be an absolute criterion for the diagnosis of a PTLD.

Clonal salivary gland infiltrates associated with myoepithelial sialadenitis (Sjögren's syndrome) begin as nonmalignant antigen-selected expansions

Myoepithelial sialadenitis (MESA) is the reactive salivary gland lymphoid infiltrate that occurs in patients with Sjogren's syndrome. Although it is well established that mucosa-associated lymphoid tissue (MALT)-type lymphomas may develop from MESA, the issue of whether monoclonal B-cell populations in early MESA-associated lesions represent MALT lymphomas or more benign types of expansions has been very controversial. In addition, it is unknown whether antigen stimulation plays a role in the development or growth of MESA-associated clones. To investigate these issues, we have analyzed the Ig VH genes used by MESA-associated clones in sequential biopsies obtained from contralateral sites of seven different patients. In three cases, single clones were identified in the follow-up biopsies that were distinct from the single clones identified in the initial specimens, whereas in three other cases, the same clone was identified in both the initial and subsequent specimens. In the remaining case, two clones were identified in the second biopsy specimen, one of which was distinct from the initial clone. Of the 11 distinct clones identified in the 14 specimens that were analyzed, 8 were derived from a V1-69 VH gene segment, whereas the other 3 were derived from a V3-7 VH gene segment. In addition, the MESA clones also showed conserved amino acids sequence motifs in their third complementarity-determining regions (CDR3), some of which were encoded by N nucleotides. The marked VH gene restriction along with the similar CDR3 sequences suggests that MESA-associated clones even from different patients may bind the same or similar antigens and are selected for clonal expansion on that basis. The high rates of ongoing VH gene mutation observed in some of the cases futher suggest that the growth of early MESA clones is still dependent on antigen stimulation. In addition, our finding that different biopsies from the same patient may contain distinct clones indicates that some MESA-associated clones have not yet evolved to malignant lymphomas.

Salivary gland lymphoid infiltrates associated with lymphoepithelial lesions: a clinicopathologic, immunophenotypic, and genotypic study

The criteria for distinguishing benign lymphoepithelial lesions (BLEL) from low grade B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) type in salivary glands and the significance of genotypically documented clonality in this setting are controversial. In addition, the clinical implications of a neoplastic diagnosis are unclear. The histopathologic features of 68 specimens from 49 patients with at least one salivary gland biopsy with LEL together with available clinical data were, therefore, reviewed. Paraffin section immunohistochemical (IHC) stains for kappa, lambda, CD3, CD20, and CD43; in situ hybridization (ISH) for kappa and lambda; and polymerase chain reaction (PCR) for immunoglobulin (Ig) HC rearrangement were performed. The 61 salivary gland specimens were classified as BLEL-13, BLEL with monocytoid B-cell (MBC) halos (BLEL-halo-8), low grade B-cell lymphoma of MALT type with confluent zones of MBC or other atypical lymphocytes (ML-MALT-24), low grade B-cell lymphoma of MALT type with monoclonal plasma cells (ML-MALT-PC-12), and high grade B-cell lymphoma of MALT type (MALT-high grade-4). Soft tissue and perineural invasion was not observed in BLEL and was most common in the MALT lymphomas. Lymph node involvement was identified in six patients at the time of their salivary gland MALT lymphomas but in none with BLEL. CD43+ B cells were seen most commonly in ML-MALT but were present in all other categories except MALT-high grade. Clonal B cells were identified by PCR in 5 of 12 BLEL, 5 of 8 BLEL-halo, 17 of 22 ML-MALT, 6 of 10 ML-MALT-PC, and 3 of 3 MALT-high grade biopsies. All ML-MALT-PC were clonal by ISH or IHC. Repeat biopsies in 14 patients most commonly showed a BLEL/ML-MALT lesion in an ipsilateral or contralateral salivary gland with one transformation to a MALT-high grade. Although only a few patients are known to have received chemoradiation or radiation therapy, most patients with low-grade lesions have pursued an indolent course. These data show the presence of two types of borderline lesions within the spectrum of lymphoid proliferations associated with salivary gland LEL. One has clonal B cells without histological features of neoplasia and the other nonconfluent MBC extending beyond the confines of LEL ("halos"). They share some features with the infrequent nonneoplastic BLEL and others with the more common low-grade B-cell lymphomas of MALT. A few high-grade B-cell lymphomas of MALT were also identified including a rare example of transformation from a low- to high-grade lesion. The optimal therapeutic approach for the borderline and low-grade lesions and the reason why so many of the lymphoproliferative lesions associated with LEL remain localized to the neck remain to be defined.

Ongoing Ig gene hypermutation in salivary gland mucosa-associated lymphoid tissue-type lymphomas

Salivary gland mucosa-associated lymphoid tissue (MALT) type lymphomas are typically indolent B-cell neoplasms that are often associated with Sjogren's syndrome. To better define the cell of origin and evaluate whether antigen receptor stimulation may be playing a role in tumor growth, the Ig heavy and light chain variable genes (VH and VL) expressed by five salivary gland MALT lymphomas were cloned and sequenced. Comparison to known germline sequences indicated that three of the lymphoma VH genes were derived from 51p1, a member of the VH1 family, while the other two used different VH gene segments from the VH3 family, 22-2B and HG19. All five of the VL genes belonged to the VkIII family, with three derived from Humkv325 and the other two from the Vg and Humkv328 genes. Numerous point mutations relative to the proposed germline genes were present in all of the lymphoma VH and VL genes. In addition, the VH and VL genes from each lymphoma showed intraclonal sequence heterogeneity indicative of ongoing somatic hypermutation. Because the process of Ig gene hypermutation is thought to occur at the germinal center stage of B-cell development, these findings suggest the MALT lymphoma cell of origin may be a germinal center B cell. Selection against mutations that result in replacement of amino acids suggested that Ig stimulation may be important for lymphoma growth. The possibility that antigen receptor stimulation may be involved in the growth of salivary gland MALT lymphomas is further suggested by the noted restricted use of VH and VL gene segments.

A clonally distinct recurrence of Burkitt's lymphoma at 15 years

A human immunodeficiency virus-negative male was successfully treated for two occurrences of Burkitt's lymphoma, 15 years apart. As consolidation of his second remission, he underwent high-dose chemotherapy with peripheral blood stem cell transplantation. In an effort to prove whether the second lymphoma was a relapse of the first or a second primary lymphoma, we obtained paraffin-embedded material from both lymphomas. DNA was extracted from this material and amplified by polymerase chain reaction (PCR) using consensus JH and VH region primers. Analysis of the PCR products, which mostly reflects VDJ joints, showed two sharp bands of different molecular size, proving the monoclonal nature of the lymphomas and suggesting that each had different Ig gene rearrangements. Sequencing of both PCR products showed a marked dissimilarity in nucleotide sequence in the clonally unique VDJ joint region, providing strong evidence for the separate cellular genesis of each lymphoma. These results suggest that late relapses of Burkitt's lymphoma should be examined for clonal distinctiveness. If the second lymphoma is distinct from the primary one, it might be treated as a primary lymphoma rather than as recurrent disease.

Transformation of mycosis fungoides: T-cell receptor beta gene analysis demonstrates a common clonal origin for plaque-type mycosis fungoides and CD30+ large-cell lymphoma

It is well recognized that patients with classical mycosis fungoides (MF) may develop a large-cell lymphoma (LCL), a phenomenon known as "transformation." An unresolved issue regarding the transformation of MF is whether MF and LCL represent two separate lymphomas or whether they are derived from the same T-cell clone. We report the clinicopathologic, immunophenotypic, and immunogenotypic analysis of MF and LCL in a white male. He developed a rash at age 51 that was diagnosed at age 56 as clinical stage IA patch/plaque MF. After topical nitrogen mustard and total skin electron beam therapy for progressive generalized CD3+CD4+ patch/plaque lesions, he developed nodules of Ki-1+ (CD30+) T-LCL at age 72. Southern blot analysis of DNA digested with Bg/II or BamHI and probed with a T-cell receptor (TCR)-beta gene J beta 1/J beta 2 probe showed a single, identical rearranged band in both the MF and LCL skin lesions that had been obtained 4 years apart. V beta gene family--specific gene amplification assays demonstrated dominant V beta 6 PCR products in both types of lesions. These PCR products and lesional cDNA exhibited a monoclonal pattern when amplified with consensus TCR-beta gene VDJ joint primers and electrophoresed under conditions that allowed the resolution of small differences in size. Furthermore, sequence analysis of the V beta 6 PCR products amplified from both the MF and LCL lesions showed an identical nucleotide sequence involving V beta 6.4, D beta 1.1, J beta 1.2, and C beta 1. These findings indicate that both the MF and the LCL in this patient arose from the same T-cell clone and that these diseases developed at a stage in the clone's differentiation subsequent to rearrangement of the TCR-beta gene.

Antigen selection in human lymphomagenesis

Although surface immunoglobulin plays a central role in the differentiation and growth of normal B-cells, its role in the growth of human B-cell malignancies is largely a matter of conjecture. Human follicular lymphomas are attractive systems to study in part because they are clones of cells sharing many similarities with germinal center B-cells which are critically dependent on antigen selection for survival. Nucleotide sequence information was determined for the immunoglobulin heavy chain variable genes expressed by two cases of follicular lymphoma. In addition, the germ line variable gene counterparts were also cloned and sequenced from biopsy material obtained from both of these patients. Numerous mutations from germ line were present in the variable genes from both of these cases, many of which accumulated during expansion and growth of these lymphomas. Moreover, the mutations that accumulated during tumor expansion were distributed in a manner that almost certainly was dependent on positive selection presumably mediated by contact with an antigen. These data indicate that antigen selection is probably important for the growth and clonal evolution of follicular lymphomas.

Clonal evolution of a follicular lymphoma: evidence for antigen selection

The potential role antigens play in growth stimulation or in clonal selection of follicular lymphomas is unknown. To study this issue, we sequenced the immunoglobulin heavy chain variable region genes expressed by a follicular lymphoma from multiple biopsy specimens and also cloned and sequenced the corresponding germ-line variable gene from this patient. Comparison to the germ-line gene revealed numerous nucleotide substitutions in all of the lymphoma variable gene sequences. Some of the substitutions may have occurred in the nonmalignant precursor B cell that gave rise to this lymphoma because they were shared among all of the variable genes, but many of the mutations accumulated as the malignant clone expanded. The mutations were distributed in such a way that strongly suggested the majority of tumor cells had been positively selected through their antigen receptor. This was especially evident for the mutations that developed late in the clonal evolution of this lymphoma. These findings indicate that antigen stimulation may be involved in the growth of follicular lymphoma tumors.

Diversity of T-cell antigen receptor variable genes used by mycosis fungoides cells

The expression of T-cell antigen receptor beta-chain variable genes (V beta) was evaluated in 28 cases of mycosis fungoides. A novel polymerase chain reaction (PCR) technique was used to associate expression of particular V beta genes with monoclonal T-cell populations. In addition, the same biopsies used for PCR analysis were also examined for reactivity with a panel of seven monoclonal antibodies that specifically recognized V beta proteins from four different families. Only three cases clearly stained with the antibodies, a result consistent with a diverse set of V beta genes being used. This was confirmed by PCR analysis, which indicated that V beta genes from many different families were expressed by these tumors. Preferential use of the V beta 8 family, which had been previously use of the V beta 8 family, which had been previously reported for this disease, was not evident among the cases analyzed.

Ig VH gene expression among human follicular lymphomas

Thirty-six randomly selected cases of low grade follicular lymphoma (FL) were analyzed for Ig heavy chain variable region (VH) gene expression. Assignment to one of the six human VH gene families (VH1 to VH6) was made with a polymerase chain reaction-based technique using family-specific leader primers. The frequency of VH family use in FL was found to be similar to that reported for normal peripheral blood lymphocytes and is therefore also roughly proportional to VH family size. To evaluate expression within an individual family, all of the lymphoma VH genes from the middle size VH4 family were sequenced and compared with previously published sequences. Of these eight lymphoma VH sequences, six were most closely related to just two of the 10 known functional VH4 germline genes. Nonrandom usage by FL of the JH3, JH4, and JH5 joining segments was also observed. Nucleotide sequences were also determined for 10 randomly selected lymphoma VH genes from the large VH3 family. With one possible exception, none of these lymphoma VH sequences appear to represent any of the VH3 genes that may be preferentially used in the fetal repertoire.

Follicular lymphoma: a model of lymphoid tumor progression in man

Human follicular lymphoma can be viewed as a malignancy in evolution. Since this disease is composed of a clonal population of B lymphocytes all expressing a given immunoglobulin light chain and heavy chain, it seems possible that the initial transforming event, the t(14; 18) chromosomal translocation, occurs in a cell already committed to the expression of a particular VH and VL gene. A panel of antibodies has been assembled which define a set of idiotypes expressed repeatedly by B-cell lymphomas. Nonetheless, VH gene usage in follicular lymphoma tumors appears to reflect the normal B-cell repertoire. Growth of follicular lymphoma appears to be partially under normal regulatory control. The expanding malignant B-cell clone grows in follicles with particular apposition to follicular dendritic cells and heavy infiltration with CD4+ T cells. Interaction with T cells can induce the proliferation of follicular lymphoma cells. This tumor eventually evolves into a diffuse large-cell lymphoma which is highly aggressive and lethal. It is now clear that the malignant progression occurs from a single cell within the expanding follicular lymphoma clone. A panel of monoclonal antibodies to cell surface molecules has been generated that inhibit proliferation of diffuse lymphoma cell lines, and some of the target molecules have been partially characterized. Therapeutic application of anti-idiotype monoclonal antibodies has shown a high degree of tumor responsiveness, but ultimately escape of idiotype-negative variant cells occurs. These variants arise as a result of extensive somatic point mutation in the VH and VL genes of follicular lymphoma. Active immunization can result in an immune response by patients directed against the idiotype expressed on their own B-cell tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular analysis of deficient class I H-2 antigen expression by mouse lung carcinoma cells

We have continued our investigations of line lung carcinoma cells to understand the molecular basis of decreased expression of class I H-2 Ag and class I Ag induction with DMSO. We show that line 1, a murine lung carcinoma cell line, has low levels of class I Ag (H-2K, D, and L) because it is deficient in both class I and beta 2-microglobulin (B2M) RNA, and that these mRNA can be coordinately induced with DMSO. Evidence presented herein also shows that IFN-gamma can induce surface expression of class I Ag and suggests that it may act through a different mechanism than DMSO in inducing class I Ag. To further evaluate the regulation of class I expression, H-2Dp genes were transfected into line 1 cells. The transfected H-2 genes appear to be constitutively expressed at much higher levels than are the endogenous class I genes because surface expression of the foreign Dp Ag on the transfectants is elevated relative to the endogenous H-2d haplotype class I Ag. Both Dp surface expression and Dp mRNA are induced after treatment with DMSO. In all the Dp transfectants, we observed higher constitutive levels of class I mRNA as well as increased constitutive levels of endogenous B2M mRNA when compared to control or untransfected line 1 cells, however, we could not correlate these constitutive levels with Dp copy number. These results suggest that the regulation of class I and B2M genes is linked and that expression of class I genes can affect the expression of B2M genes.

Molecular analysis of deficient class I H-2 antigen expression by mouse lung carcinoma cells

We have continued our investigations of line lung carcinoma cells to understand the molecular basis of decreased expression of class I H-2 Ag and class I Ag induction with DMSO. We show that line 1, a murine lung carcinoma cell line, has low levels of class I Ag (H-2K, D, and L) because it is deficient in both class I and beta 2-microglobulin (B2M) RNA, and that these mRNA can be coordinately induced with DMSO. Evidence presented herein also shows that IFN-gamma can induce surface expression of class I Ag and suggests that it may act through a different mechanism than DMSO in inducing class I Ag. To further evaluate the regulation of class I expression, H-2Dp genes were transfected into line 1 cells. The transfected H-2 genes appear to be constitutively expressed at much higher levels than are the endogenous class I genes because surface expression of the foreign Dp Ag on the transfectants is elevated relative to the endogenous H-2d haplotype class I Ag. Both Dp surface expression and Dp mRNA are induced after treatment with DMSO. In all the Dp transfectants, we observed higher constitutive levels of class I mRNA as well as increased constitutive levels of endogenous B2M mRNA when compared to control or untransfected line 1 cells, however, we could not correlate these constitutive levels with Dp copy number. These results suggest that the regulation of class I and B2M genes is linked and that expression of class I genes can affect the expression of B2M genes.

Lysis of a lung carcinoma by poly I:C-induced natural killer cells is independent of the expression of class I histocompatibility antigens

Cells from the line 1 murine carcinoma express little if any H-2d when grown in normal medium. These cells are susceptible to splenic cell populations with NK activity, stimulated by prior injection of poly I:C, but are not lysed by NK-deficient splenocytes from homozygous beige mice treated with anti-asialo GM1. Incubation of line 1 cells in medium containing DMSO leads to a dramatic stimulation of H-2d expression but no change in lytic susceptibility to splenic NK cells. Transfection of H-2Dp into line 1 leads to a constitutive and DMSO-inducible expression of H-2Dp at functionally significant levels, but this expression appears to have no influence on NK cytolytic susceptibility.

Lysis of a lung carcinoma by poly I:C-induced natural killer cells is independent of the expression of class I histocompatibility antigens

Cells from the line 1 murine carcinoma express little if any H-2d when grown in normal medium. These cells are susceptible to splenic cell populations with NK activity, stimulated by prior injection of poly I:C, but are not lysed by NK-deficient splenocytes from homozygous beige mice treated with anti-asialo GM1. Incubation of line 1 cells in medium containing DMSO leads to a dramatic stimulation of H-2d expression but no change in lytic susceptibility to splenic NK cells. Transfection of H-2Dp into line 1 leads to a constitutive and DMSO-inducible expression of H-2Dp at functionally significant levels, but this expression appears to have no influence on NK cytolytic susceptibility.