Genetic Characteristics of Non B Cell-Derived Immunoglobulin Genes.

It is widely acknowledged that immunoglobulins (Igs) are produced solely by B-lineage cells. The Ig gene is created by the rearrangement of a group of gene segments [variable (V), diversity (D), and joining (J) segments rearrangement, or V(D)J recombination], which results in the vast diversity of B cell-derived Ig responsible for recognising various antigens. Ig subsequently undergoes somatic hypermutation (SHM) and class switch recombination (CSR) after exposure to antigens, thus converting the low-affinity IgM to IgG, IgA, or IgE antibodies. IgM and IgD are primarily expressed in naïve B cells that have not been exposed to antigens, they do not undergo somatic hypermutation; hence, their variable region sequences remain the same as those in the germline. In contrast, IgG, IgA, and IgE are expressed in antigen-stimulated memory B cells or plasma cells, and thus, they often possess high-frequency mutations in their variable region sequences. Since the discovery that Ig can be produced by non-B cells, Qiu's group has investigated and compared the genetic characteristics of B cell-derived Ig and non-B cell-derived Ig. These findings demonstrated that non-B cell-derived Ig shares certain similarities with B cell-derived Ig in that the sequence of its constant region is identical to that of B cell-derived Ig, and its variable region is also strictly dependent on the rearrangement of V, D, and J gene segments. Moreover, akin to B cell-derived Ig, the V regions of IgM and IgD are rarely mutated, while IgG, IgA, and IgE produced by cancer cells are frequently mutated. However, the non-B cell-derived Ig V region sequence displays unique characteristics. (1) Unlike the vast diversity of B cell-derived Igs, non-B cell-derived Igs exhibit restricted diversity; cells from the same lineage always select the same V(D)J recombination patterns; (2) Both mRNA and proteins of RAG1/RAG2 recombinase have been detected in Ig positive cancer cell lines and normal tissues. But Ig recombination could also be found in RAG1-/- and RAG2-/- mice, suggesting that they are not necessary for the rearrangement of non-B cell-derived Igs. These features of non-B cell-derived Igs suggest a potentially undiscovered mechanism of V(D)J recombination, ligation, and SHM in non-B cells, which necessitates further investigation with advanced technology in molecular biology.

Persistence of monoclonal B-cell expansion and intraclonal diversification despite virus eradication in patients affected by hepatitis C virus-associated lymphoproliferative disorders.

We investigated 23 hepatitis C virus (HCV)-infected patients with overt lymphoproliferative diseases (15 cases) or monoclonal B lymphocytosis (8 cases) treated with direct agent antiviral (DAAs) per clinical practice. DAA therapy yielded undetectable HCV-RNA, the complete response of cryoglobulinemia vasculitis and related signs, whilst the presence of B-cell clones (evaluated by flow cytometry, IGHV, and BCL2-IGH rearrangements), detected in 19/23 cases at baseline, was maintained (17/19). Similarly, IGHV intraclonal diversification, supporting an antigen-driven selection mechanism, was identified in B-cell clones at baseline and end of follow-up. DAA therapy alone, despite HCV eradication and good immunological responses, was less effective on the pathological B-cell clones.

Deciphering molecular complexity of HCV-associated lymphoproliferation.

Recent clinical studies demonstrated the achievement of lymphoma responses in patients with Hepatitis C virus-associated indolent lymphoproliferative disorders (LPD) receiving direct-acting antivirals (DAAs) as their sole treatment. However, the molecular mechanisms underlying LPD responses to DAAs are still poorly understood. In their paper the authors provide new molecular insights on this issue, reporting intraclonal diversification and persistence of B-cell clones in most cases, despite viral eradication and beneficial clinical outcome. These provocative data suggest that the achievement of molecular response is probably not required for a 'functional cure' of these patients. Further comprehensive immunogenetic and mutational studies would be fundamental to dissect this biological puzzle and, ultimately, to refine improved treatment strategies in this setting. Commentary on: Mazzaro et al. Persistence of monoclonal B-cell expansion and intraclonal diversification despite virus eradication in patients affected by hepatitis C virus-associated lymphoproliferative disorders. Br J Haematol 2023;203:237-243.

Ultra-low frequency labeling of single cell lineages in Drosophila.

We describe a new methodology for genetically labeling single cell lineages in Drosophila called DMARCM. The system offers ultra-low frequency labeling, linear induction, consistent labeling among individuals and virtually no background signal. We compare this technique to an existing approach, which has been widely adopted. We demonstrate how application of DMARCM in the gastrointestinal epithelium permits the effects of labeling frequency on tumorigenic stem cell growth to be distinguished in an established tumor model.

Single-cell transcriptome analyses reveal heterogeneity in suspension cultures and clonal markers of CHO-K1 cells.

Cell-to-cell variability in cell populations arises from a combination of intrinsic factors and extrinsic factors related to the milieu. However, the heterogeneity of high cell density suspension cultures for therapeutic protein production remains unknown. Here, we illustrate the increasing heterogeneity in the cellular transcriptome of serum-free adapted CHO K1 cells during high cell density suspension culture over time without concomitant changes in the genomic sequence. Cell cycle-dependent subpopulations and cell clusters, which typically appear in other single-cell transcriptome analyses, were not found in these suspension cultures. Our results indicate that cell division changes the intracellular microenvironment and leads to cell cycle-dependent heterogeneity. Whole mitochondrial single-cell genome sequencing showed cell-to-cell mitochondrial genome variation and heteroplasmy within cells. The mitochondrial genome sequencing method developed here is potentially useful for the validation of cell clonality. The culture time-dependent increase in cellular heterogeneity observed in this study did not show any attenuation in this increasing heterogeneity. Future advances in bioengineering such as culture upscaling, prolonged culturing, and complex culture systems will be confronted with the need to assess and control cellular heterogeneity, and the method described here may prove useful for this purpose.

Genome-wide analysis of single nucleotide variants allows for robust and accurate assessment of clonal derivation in cell lines used to produce biologics.

A clonally derived (or "monoclonal") cell line is a cell population derived from a single progenitor cell. Clonally derived cell lines are required for many biotechnological applications. For instance, recombinant mammalian cells used to produce therapeutic proteins are expected by regulatory authorities to be clonally derived. Assurance of clonal derivation (or "clonality") is usually obtained from the characterization of the procedure used for cell cloning, for instance by assessing the success rate of single-cell sorting but not by assessing the cell line itself. We have developed a method to assess clonal derivation directly from the genetic makeup of cells. The genomic test of clonality is based on whole-genome sequencing and statistical analysis of single nucleotide variants. This approach quantifies the clonal fractions present in nonclonal samples and it provides a measure of the probability that a cell line is derived from a single cell. Upon experimental validation of the test, we show that it is highly accurate and that it can robustly detect minor clonal fractions of as little as 1% of the cell population. Moreover, we find that it is applicable to various cell line development protocols. This approach can simplify development protocols and shorten timelines while ensuring clonal derivation with high confidence.

Detection of monoclonal free light chains by immunofixation electrophoresis and isoelectric focusing - comparison with the quantitative method of determination.

The study aimed to investigate free light chain (FLC) monoclonality in patients with an abnormal free kappa/lambda ratio (FLC ratio). Seventy serum samples with abnormal FLC ratio were examined using an immunoturbidimetry (Binding Site, SPA) and the two different enzyme-linked immunosorbent assays (1. Sebia diagnostic kit; 2. in house methods), the monoclonal or oligoclonal bands of (FLC) by immunofixation electrophoresis (IE) and isoelectric focusing followed by affinity immunoblotting (IEF/AIB). The reference interval was calculated by non-parametric percentile method. 5.7% of samples examined by IE were suspected of monoclonal character of FLCs, but subsequently monoclonality was refuted by more sensitive IEF/AIB method; 7%, resp. 2.9% of samples showed FLC kappa, resp. FLC lambda oligoclonal character of bands. A statistically significant dependence was found between FLC ratio (Sebia) and FLC ratio (SPA), rs = 0.510, p = .001. Kappa statistic evaluated a fair conformity between the FLC ratio (Sebia) and IEF/AIB (kappa = 0.468) and between FLC ratio (in house) and IEF/AIB (kappa = 0.300). The verified reference interval for FLC ratio (Binding Site) is between 0.35 and 2.18. The IEF/AIB is the most sensitive method to discriminate between monoclonal and oligoclonal bands of FLC. The Binding Site and Sebia diagnostic kits do not give consistent results. The Binding Site diagnostic kit provides more results above reference interval of FLC ratios. For routine decision on monoclonality of the FLC ratio (SPA) it is advisable to use a verified reference interval.

Rapid in-situ hybridization and immunohistochemistry: a pilot comparative study of two rapid diagnostic techniques for establishing monoclonality in plasma cell dyscrasias.

BACKGROUND: Light chain restriction needs to be established on the paraffin embedded tissue in certain types of plasma cell dyscrasias when serum levels of monoclonal immunoglobulins and light chain assays in the urine and serum may be normal. Rapid-in-situ-hybridisation (RISH) is thought to be a superior to immunohistochemistry (IHC) for kappa and lambda staining due to brighter and crisp staining without any background. METHODS: Fifty cases were included in this pilot study. Serum light chain restriction status of the case was taken as gold standard. The results of standard IHC for kappa and lambda immunoglobulins on the bone marrow biopsy of these cases was compared with RISH performed by the two commercially available kits. The results of the two methods were compared for sensitivity, need to repeat the test and background staining. RESULTS: The study found that in IHC first run sensitivity was 58% which improved to 88% after the second run. For RISH the sensitivity was 100%. CONCLUSION: Rapid-in-situ-hybridisation (RISH) is a superior technique to IHC for detecting kappa and lambda light chain in plasma cells. The test is as labour intensive and time consuming as the routine IHC but has no background staining with more bright and crisp staining quality.

Treatment-associated outcomes of patients with primary ocular adnexal MALT lymphoma after accurate diagnosis.

BACKGROUND: Differentiation between primary ocular adnexal mucosa-associated lymphoid tissue (POA-MALT) lymphoma and reactive lymphoid hyperplasias sometimes may be difficult. We have examined the treatment-associated mortality of POA-MALT lymphoma after confirmed diagnosis and evaluated their proper treatments. PATIENTS AND METHODS: From 1991 through 2016, cases of POA-MALT lymphoma were retrospectively analyzed based on their pathological and molecular/immunological diagnoses. RESULTS: A total of 78 cases with POA-MALT lymphoma with a median age of 66 years were analyzed over median/mean observations of 6.4/7.1 years. Forty-four patients (56%) were diagnosed with IgH gene clonality and 10 patients (13%) were diagnosed with flow cytometric analysis in addition to the pathological decision. The rest (24 patients, 31%) were diagnosed employing pathological decisions of hemato-pathologists and clinical decisions. All patients, except cases of watchful waiting, achieved complete remission. After initial treatment, 68 patients (87%) presented disease-free during the observation period. As treatment, a radiotherapy-based strategy was followed with 15 patients (19%, group A). Immuno-chemotherapy was administered to 24 patients (31%, B). Surgical extraction only was selected for 36 patients (46%, C). Watchful waiting was selected with three patients (4%). Recurrence after the initial treatment was found in one patient (7%) out of A, in three patients (13%) out of B, and in six patients (17%) out of C, respectively. Progression-free survivals at 5 and 10 years were 100 and 100% in A, 95 and 75% in B, and 88 and 81% in C, respectively. The recurrence rates between the patients who were diagnosed with only pathological decision (n = 24) and the patients who were diagnosed with molecular and immunological procedures (n = 54) did not show any statistical differences. CONCLUSION: Our results indicate that radiotherapy-based treatment strategies for patients with POA-MALT lymphoma show a low rate of recurrence and may improve their prognosis even after the accurate diagnosis. However, contamination of the cases with reactive (polyclonal) lymphoid hyperplasia into those with MALT lymphoma should be carefully removed to avoid unnecessary treatment for malignancies that do not exist.

A rapid single cell sorting verification method using plate-based image cytometry.

Single cell sorting is commonly used for ensuring monoclonality and producing homogenous target cell populations. Current single cell verification methods involve manually confirming the existence of single cells or colonies in a well using a standard light microscope. However, the manual verification method is time-consuming and highly tedious, which prompts a need for an accurate and rapid detection method for verifying single cell sorting capability. Here, we demonstrate a rapid single cell sorting verification method using the Celigo Image Cytometer. Calcein AM-stained Jurkat cells and fluorescent beads are sorted into 96-well half area microplates using the MoFlo Astrios EQ. Whole well bright field and fluorescent images are acquired and analyzed using the image cytometer in less than 8 min. The proposed single cell verification detection method in multi-well microplates can allow for quick optimization of FACS instruments at flow core laboratories, as well as improvement of downstream biological assays by accurately confirming the presence of single cells in each well.

A case of combined small cell lung carcinoma with unique morphology: Investigation of tumorigenesis.

Small cell lung carcinoma (SCLC) usually grows in a pure form with no other associated histological components. However, combined small cell lung carcinoma (cSCLC), which is accompanied by other histological components (cSCLCs) may sometimes occur. Herein, we analyzed the tumorigenesis of cSCLC containing a demarcated area of pure SCLC. A 76-year-old man had a 25-mm mass in the perihilar portion of his right upper lung. Histologically, the cSCLC contained two relatively demarcated areas: one area composed of pure SCLC cells and another area of SCLC, squamous-like component (SLC), and spindle cell carcinoma (SpCC) cells. Loss of heterozygosity (LOH) was observed at allele 3p in all tumor components and at 22q in the pure SCLC component. Histological and immunohistochemical analysis and LOH study suggested that all components were likely to be monoclonal in origin and revealed that the pure SCLC component was not the precursor of the cSCLC. In the tumorigenesis of this case, the pure SCLC and the cSCLC may have originated from a common pluripotent tumor cell and then diverged, although we cannot state this conclusively. Further studies with more cases are necessary to test this theory.

Clinicopathological analysis of proliferative glomerulonephritis with monoclonal IgG deposits in 5 renal allografts.

BACKGROUND: We present a case series of 5 patients with proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) of renal allografts to better define its natural history, presenting characteristics, pathological features and treatment outcome. RESULTS: These 5 patients presented 5 to 19 months post-kidney transplantation for complaints of serum creatinine (Scr) elevation, proteinuria or hematuria. Membranoproliferative glomerulonephritis (MPGN) pattern was the most frequently observed histological manifestation. Immunofluorescence showed monoclonal IgG3κin 3 patients and IgG3λ in the other 2 cases. Immunofluorescence staining helped to establish PGNMID in the absence of conspicuous microscopic changes in one case. Rituximab and bortezomib were effective in alleviating proteinuria in all 4 treated patients and decreasing Scr in 2 cases. Plasmapheresis treatment in another patient was not effective in preventing Scr elevation. At last-follow-up, 2 patients were in dialysis and 2 had improved kidney function with almost normal Scr and no proteinuria. The remaining one patient died of pulmonary infections. CONCLUSIONS: We conclude that PGNMID occurs early after kidney transplant. PGNMID should be included in the differential diagnoses of recurrent MPGN in renal allografts. Rituximab and bortezomib are helpful to decrease proteinuria and Scr in a subset of patients. Larger studies are needed to conclusively establish best treatment strategies for PGNMID in renal allografts.

[Two cases of proliferation of monoclonal and monotypic lymphocytes and plasma cells corresponding to acrodermatitis chronica atrophicans]. / Prolifération cutanée lympho-plasmocytaire monoclonale et monotypique révélant une acrodermatite chronique atrophiante : deux observations.

BACKGROUND: While a dermal proliferation of monotypic monoclonal lymphocytes and plasma cells suggests above all cutaneous marginal zone lymphoma (CMZL) or plasmacytoma, it may also correspond to a Borrelia infection of which the clinic picture is evocative, as demonstrated in the cases presented herein. PATIENTS AND METHODS: The files of two patients were submitted for discussion at the regional multidisciplinary staff meeting on cutaneous lymphomas after review of the skin biopsies led to a diagnosis of plasmacytoma and CMZL on the basis of infiltrate containing abundant plasma cells. The infiltrates of both patients showed a kappa monotypic light chain and cutaneous B-cell clones were detected. However, the clinical features, with monomelic maculopapular rash, were evocative primarily of Borrelia infection. Diagnosis was confirmed by positive serology and clinical cure was achieved after 3 weeks of oral tetracycline, without relapse. COMMENTS: A link between Borrelia infection and cutaneous lymphomas has long been thought to exist. Further, it is recommended that antibiotics be considered in CMZL before undertaking systemic therapy. The classic histological appearance of the tertiary phase of early-stage Lyme's disease shows perivascular and periadnexal infiltrate comprising lymphocytes and plasma cells. At the later stages, epidermal atrophy occurs with thinning of the dermis. The monoclonal and monotypic nature of skin proliferation points above all to CMZL or plasmacytoma. However, clinicopathological correlation is an essential step before such a diagnosis may be made. In the event of monomelic erythema, as in our patients, it is important to screen for Borrelia infection, which responds well to appropriate treatment.

Generation of Monoclonal Chinese Hamster Ovary Cell Lines Using DISPENCELL-S3.

Single-cell isolation is a key step in the manufacturing of therapeutic proteins, which relies on the development of monoclonal cell lines. It increases production safety and consistency. It also ensures higher manufacturing performances thanks to the selection of the rare clonally derived cell lines with optimal growth and production capacities. DISPENCELL-S3 is a small format single-cell dispenser whose technology is based on impedance spectroscopy. Here, we provide a detailed protocol for generating Chinese hamster ovary (CHO) monoclonal cell lines using DISPENCELL-S3. Production and characterization of an adequate cell sample for single-cell isolation, as well as the optimization of the DISPENCELL-S3 dispensing parameters are described. Monoclonal outgrowth assessment and the use of the recorded impedance signal as evidence of clonality are also outlined.

Evaluation of laboratory diagnostic tests for light-chain clonality and bone marrow findings in AL amyloidosis.

Background: Light-chain amyloidosis (AL) is the most common form of systemic amyloidosis. This study aimed to evaluate the usefulness of laboratory tests for light-chain clonality and bone marrow (BM) findings in AL amyloidosis. Methods: We retrospectively enrolled patients newly diagnosed with AL amyloidosis on pathological examination who underwent a BM biopsy. Laboratory test data for light-chain clonality were collected and compared. Amyloid deposits were identified with H&E, Congo red, and PAS stains. Results: We reviewed 98 patients with AL amyloidosis. Light chain clonality (λ, 64 cases; κ, 34 cases) was detected by serum immunofixation electrophoresis (IFE) (63.3%), urine IFE (70.8%), serum protein electrophoresis (PEP) (44.9%), urine PEP (44.8%), serum free light chain (SFLC) ratio (79.5%), and BM immunohistochemistry (IHC) (85.7%). Flow cytometric (FCM) assay identified aberrant BM plasma cells in 92.9% of cases. BM amyloid deposits were identified in 35 of the 98 cases (35.7%); 71.4% (25/35) were Congo red-positive, and 100.0% (35/35) were PAS-positive. Conclusion: Laboratory tests for detecting light-chain clonality in AL amyloidosis in order of sensitivity include FCM assay for aberrant plasma cells, IHC for light chains on BM biopsy or clot section, SFLC ratio, and serum and urine IFE. Congo red staining of BM samples remains an important tool for identifying amyloid deposits in BM. Periodic acid-Schiff (PAS) staining can be useful in diagnosing some cases of Congo red-negative amyloidosis.

Mixed Pulmonary Adenocarcinoma and Atypical Carcinoid: A Report of Two Cases of a Non-codified Entity With Biological Profile.

Pulmonary carcinoids combined with a non-neuroendocrine component have rarely been described, and this histological subtype is not included as a specific entity in the current World Health Organization classification of pulmonary neoplasms. Here, we described the molecular and histological features of two rare cases of mixed lung neoplasms, composed of atypical carcinoid and adenocarcinoma. The targeted next-generation sequencing analysis covering single nucleotide variations, copy number variations, and transcript fusions in a total of 161 cancer genes of the two different tumor components shows a similar molecular profile of shared and private gene mutations. These findings suggest their monoclonal origin from a transformed stem/progenitor tumor cell, which acquires a divergent differentiation during its development and progression and accumulates novel, specific mutations.

High-throughput and automation advances for accelerating single-cell cloning, monoclonality and early phase clone screening steps in mammalian cell line development for biologics production.

Mammalian cell line development is a multistep process wherein timelines for developing clonal cells to be used as manufacturing cell lines for biologics production can commonly extend to 9 months when no automation or modern molecular technologies are involved in the workflow. Steps in the cell line development workflow involving single-cell cloning, monoclonality assurance, productivity and stability screening are labor, time and resource intensive when performed manually. Introduction of automation and miniaturization in these steps has reduced the required manual labor, shortened timelines from months to weeks, and decreased the resources needed to develop manufacturing cell lines. This review summarizes the advances, benefits, comparisons and shortcomings of different automation platforms available in the market for rapid isolation of desired clonal cell lines for biologics production.

Retrospective assessment of clonal origin of cell lines.

Cell lines used for the manufacture of recombinant proteins are expected to arise from a single cell as a control strategy to limit variability and ensure consistent protein production. Health authorities require a minimum of two rounds of limiting dilution cloning or its equivalent to meet the requirement of single cell origin. However, many legacy cell lines may not have been generated with process meeting this criteria potentially impeding the path to commercialization. A general monoclonality assessment strategy was developed based on using the site of plasmid integration for a cell's identity. By comparing the identities of subclones from a master cell bank (MCB) to each other and that of the MCB, a probability of monoclonality was established. Two technologies were used for cell identity, Southern blot and a PCR assay based on plasmid-genome junction sequences identified by splinkerette PCR. Southern blot analysis revealed that subclones may have banding patterns that differ from each other and yet indicate monoclonal origin. Splinkerette PCR identifies cellular sequence flanking the point(s) of plasmid integration. The two assays together provide complimentary data for cell identity that enables proper monoclonality assessment and establishes that the three legacy cell lines investigated are all of clonal origin.

Using Fluid Walls for Single-Cell Cloning Provides Assurance in Monoclonality.

Single-cell isolation and cloning are essential steps in many applications, ranging from the production of biotherapeutics to stem cell therapy. Having confidence in monoclonality in such applications is essential from both research and commercial perspectives, for example, to ensure that data are of high quality and regulatory requirements are met. Consequently, several approaches have been developed to improve confidence in monoclonality. However, ensuring monoclonality using standard well plate formats remains challenging, primarily due to edge effects; the solid wall around a well can prevent a clear view of how many cells might be in a well. We describe a method that eliminates such edge effects: solid confining walls are replaced by transparent fluid ones, and standard low-cost optics can confirm monoclonality.

Mycosis Fungoides, Lymphomatoid Papulosis and Hodgkin's Lymphoma in the Same Patient: Apropos of a Possible Monoclonal Origin.

A 59-year-old man with Hodgkin's lymphoma was referred by a hematologist for consultation for cutaneous issues. Physical examination revealed generalized scaling and erythematous scaly patches located in the groin, abdomen, and arms. The biopsy was compatible with mycosis fungoides (MF). At his next medical visit, painful nodules with erythematous halo and scabby surface were noted, and a subsequent biopsy was compatible with lymphomatoid papulosis (LyP). Mycosis fungoides, the most common primary cutaneous T-cell lymphoma, is usually defined in its classic form as a CD4+ non-Hodgkin lymphoma; LyP corresponds to a CD30+ lymphoproliferative disorder; and Hodgkin's lymphoma (HL) constitutes a lymphoid neoplasia characterized by the presence of Reed-Sternberg cells and its variants. Although these entities have been defined independently, evidence suggests the possibility of a common monoclonal origin. To our knowledge, this is the first case of MF, LyP, and HL in a single patient.