Comparative Study on the Clinicopathologic and Molecular Characteristics of Primary and Secondary Diffuse Large B-cell Lymphoma in the Central Nervous System.

BACKGROUND/AIM: Diffuse large B-cell lymphoma of the central nervous system (CNS-DLBCL) is an aggressive B-cell lymphoma with clinical and molecular heterogeneity. Primary CNS-DLBCL (PCNSL) affects the brain, eyes, leptomeninges, or spinal cord without systemic involvement. Secondary CNS-DLBCL (SCNSL) manifests concurrently with systemic lymphoma or as an isolated CNS relapse with poor prognosis. MATERIALS AND METHODS: Next-generation sequencing (NGS) was used to identify genomic alterations in 32 PCNSL and 9 SCNSL cases. Single nucleotide variants and copy number variations in addition to the clinicopathologic data and proposed risk predictive values were compared to aid in diagnostic differentiation between the two types of lymphomas. RESULTS: The MCD genotype, characterized by mutations in MYD88 and CD79B, is the most common alteration in PCNSL and is associated with lower survival rates. The frequency of MYD88 mutation was significantly higher in PCNSL compared to SCNSL (75.0% vs. 33.3%; p=0.042). Recurrent copy number loss of 6p21 occurred in 56.1% of cases, more often in PCNSL (65.6%) than in SCNSL (22.2%) (p=0.028). Diagnostic positive predictive values (PPV) of MYD88 mutation and 6p21 loss for PCNSL were 89% and 91%, respectively. PPV of both alterations was 93% for the diagnosis of PCNSL. CONCLUSION: MYD88 mutation and 6p21 loss were significantly higher in PCNSL than in SCNSL, and novel risk prediction models based on these distinct genomic profiles can aid in the clinical differentiation of PCNSL and SCNSL.

Fluoxetine Successfully Treats Intracranial Enterovirus E18 Infection in a Patient with CD79a Deficiency Arising from Segmental Uniparental Disomy of Chromosome 19.

The pre BCR complex plays a crucial role in B cell production, and its successful expression marks the B cell differentiation from the pro-B to pre-B. The CD79a and CD79b mutations, encoding Igα and Igß respectively, have been identified as the cause of autosomal recessive agammaglobulinemia (ARA). Here, we present a case of a patient with a homozygous CD79a mutation, exhibiting recurrent respiratory infections, diarrhea, growth and development delay, unique facial abnormalities and microcephaly, as well as neurological symptoms including tethered spinal cord, sacral canal cyst, and chronic enteroviral E18 meningitis. Complete blockade of the early B cell development in the bone marrow of the patient results in the absence of peripheral circulating mature B cells. Whole exome sequencing revealed a Loss of Heterozygosity (LOH) of approximately 19.20Mb containing CD79a on chromosome 19 in the patient. This is the first case of a homozygous CD79a mutation caused by segmental uniparental diploid (UPD). Another key outcome of this study is the effective management of long-term chronic enteroviral meningitis using a combination of intravenous immunoglobulin (IVIG) and fluoxetine. This approach offers compelling evidence of fluoxetine's utility in treating enteroviral meningitis, particularly in immunocompromised patients.

Deciphering the Prognostic Significance of MYD88 and CD79B Mutations in Diffuse Large B-Cell Lymphoma: Insights into Treatment Outcomes.

BACKGROUND: The clinical and genetic characteristics, as well as treatment outcomes, of diffuse large B-cell lymphoma (DLBCL) patients with different MYD88 and CD79B mutation status merit further investigation. OBJECTIVE: This study aims to investigate the distinctions in clinical manifestations, genetic characteristics, and treatment outcomes among MYD88-CD79Bco-mut, MYD88/CD79Bsingle-mut, and MYD88-CD79Bco-wt DLBCL patients. PATIENTS AND METHODS: Clinical and genetic characteristics, along with treatment outcomes among 2696 DLBCL patients bearing MYD88-CD79Bco-mut, MYD88/CD79Bsingle-mut, and MYD88-CD79Bco-wt treated with R-CHOP/R-CHOP-like regimens from the Cancer Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College and six external cohorts were analyzed. Potential molecular mechanisms were investigated through Gene Set Enrichment Analysis and xCell methodology. RESULTS: In the MCD subtype, patients with MYD88-CD79Bco-mut showed comparable progression-free survival (PFS) and overall survival (OS) compared to MYD88/CD79Bsingle-mut or MYD88-CD79Bco-wt. However, in the non-MCD subtype, patients with MYD88-CD79Bco-mut exhibited significantly inferior OS than MYD88/CD79Bsingle-mut or MYD88-CD79Bco-wt, while there was no significant OS difference between MYD88/CD79Bsingle-mut and MYD88-CD79Bco-wt (median OS: 68.8 [95% CI 22-NA] vs NA [95% CI 112-NA] vs 177.7 [95% CI 159-NA] months; MYD88-CD79Bco-mut vs MYD88/CD79Bsingle-mut: p = 0.02; MYD88-CD79Bco-mut vs MYD88-CD79Bco-wt: p = 0.03; MYD88/CD79Bsingle-mut vs MYD88-CD79Bco-wt: p = 0.33). Regarding patients with MYD88-CD79Bco-mut, there was no significant difference in PFS and OS between the MCD and non-MCD subtypes. Within the MYD88-CD79Bco-mut group, patients with PIM1mut had better PFS than PIM1wt (median PFS: 8.34 [95% CI 5.56-NA] vs 43.8 [95% CI 26.4-NA] months; p = 0.02). Possible mechanisms contributing to the superior PFS of PIM1mut patients may include activated lymphocyte-mediated immunity and interferon response, a higher proportion of natural killer T cells and plasmacytoid dendritic cells, as well as suppressed angiogenesis and epithelial-mesenchymal transition, along with lower fibroblast and stromal score. CONCLUSIONS: In the MCD subtype, patients with MYD88-CD79Bco-mut showed comparable PFS and OS compared to MYD88/CD79Bsingle-mut or MYD88-CD79Bco-wt, while in the non-MCD subtype, they exhibited significantly inferior OS. There was no significant disparity in PFS and OS of MYD88-CD79Bco-mut between the MCD and non-MCD subtypes. The presence of PIM1mut within the MYD88-CD79Bco-mut group correlated with better PFS, which may result from an intricate interplay of immune processes and tumor microenvironment alterations.

A single-centre, real-world study of BTK inhibitors for the initial treatment of MYD88mut /CD79Bmut diffuse large B-cell lymphoma.

BACKGROUND: MCD (MYD88L265P /CD79Bmut ) diffuse large B-cell lymphoma has a poor prognosis. There is no published clinical research conclusion regarding zanubrutinib or orelabrutinib for the initial treatment of MCD DLBCL. AIMS: This study aimed to analyse the efficacy and safety of Bruton's tyrosine kinase inhibitor (BTKi) (zanubrutinib or orelabrutinib) therapy for newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut . MATERIALS AND METHODS: Twenty-three newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut from June 2020 to June 2022 received BTKi combined with rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) or rituximab + lenalidomide (R2 ). A control group of 17 patients with MYD88mut and/or CD79Bmut DLBCL who received the standard R-CHOP therapy was also assessed. We retrospectively analysed clinical characteristics, safety, overall response rate (ORR), complete response (CR) rate and progression-free survival (PFS) of the two groups. RESULTS: The main clinical features were a high International Prognostic Index (IPI) score (≥3, 22/40, 55%) and a high rate of extranodal involvement (27/40,67.5%). Among the 23 DLBCL patients, 18 received BTKi + R-CHOP, and five elderly DLBCL patients were treated with BTKi + R2 . Compared with those in the control group (ORR 70.6%, CRR 52.9%, 1-year PFS rate 41.2%), improved ORR, CRR and PFS results were observed in the BTKi + R-CHOP group (100%, 94.4% and 88.9%, p = 0.019, 0.007, and 0.0001). In subgroup analyses based on genetic subtypes, cell origin, dual expression or IPI score, patients in the BTKi + R-CHOP group had better PFS than patients in the control group. In the BTKi + R-CHOP group, no significant difference was found in ORR, CRR and PFS based on subtype analysis, while BTKi-type subgroups exhibited statistically significant differences in 1-year PFS (p = 0.028). There were no significant differences in grade 3-4 haematological toxicity (p = 1) and grade 3-4 non-haematological toxicity (p = 0.49) between the BTKi + R-CHOP and R-CHOP treatment groups. In the BTKi + R2 group, the ORR was 100%, the CRR was 80%, and the 1-year PFS rate was 80%. The incidences of grade 3-4 haematologic toxicity and non-haematological toxicity were both 40%. No bleeding or cardiovascular events of grade 3 or higher occurred in any patients. DISCUSSION: The efficacy of BTKi combined with R-CHOP was similar to previous reports, which was significantly better than R-CHOP alone. It is necessary to fully consider that 14 patients in the BTKi + R-CHOP group received a BTKi as maintenance therapy when evaluating efficacy. Meanwhile, the addition of a BTKi may improve the prognosis of non-GCB, DEL or high-IPI-score DLBCL patients with MYD88mut and/or CD79Bmut . In our study, five elderly DLBCL patients with MYD88mut and/or CD79Bmut were achieved better ORR, CRR, PFS than the historical data of R-miniCHOP treatment and Ibrutinib + R2 treatment. However, the efficacy and benefit of BTKis for this type of DLBCL need to be further analysed using a larger sample size. CONCLUSION: This study suggests that newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut may benefit from BTKis according to real-world clinical data.

Nomogram for predicting survival of patients with diffuse large B-cell lymphoma.

The international prognostic index (IPI) system has been widely used to predict prognosis in diffuse large B-cell lymphoma (DLBCL). However, this system categorizes DLBCL patients into four risk groups, and cannot optimize individualized prognosis. In addition, other clinicopathological factors, such as molecular aberrations, are not incorporated into the system. To partly overcome these weak points, we developed nomograms to predict individual patient survival. We also incorporated MYD88L265P and CD79BY196 mutations into the nomograms since these mutations are associated with a worse prognosis and their signaling pathways have been highlighted as a therapeutic target. We analyzed 302 DLBCL cases for which multivariate analysis by Cox proportional hazard regression was performed. Nomograms for progression-free survival (PFS) and overall survival (OS) were constructed and assessed by a concordance index (C-index). The nomograms were also evaluated using an open external dataset (n = 187). The MYD88L265P and/or CD79BY196 (MYD88/CD79B) mutation was detected in 62/302 patients. The nomograms incorporating IPI factors exhibited a C-index of 0.738 for PFS and a C-index of 0.765 for OS. The nomograms incorporating IPI factors and the MYD88/CD79B mutation showed a C-index of 0.745 for PFS and a C-index of 0.769 for OS. The nomograms we created were evaluated using an external dataset and were well validated. The present nomograms incorporating IPI factors and the MYD88/CD79B mutation have sufficient discrimination ability, and may effectively predict prognosis in DLBCL patients. The prognostic models we have presented here may help clinicians personalize prognostic assessments and clinical decisions.

Diagnostic methods for primary vitreoretinal lymphoma: A systematic review.

Primary vitreoretinal lymphoma is a potentially aggressive intraocular malignancy with poor systemic prognosis and sometimes significant diagnostic delays as it may masquerade as chronic uveitis. Despite the variety of diagnostic techniques, it is unclear which modality is most accurate in the diagnosis of PVRL. A systematic literature search was conducted on Ovid MEDLINE, EMBASE and the Cochrane Controlled Register of Trials for studies published between January, 2000, and June, 2023. Randomized controlled trials (RCTs) reporting on the following diagnostic tools used to diagnose patients with PVRL were included: cytology, flow cytometry, MYD88 L265P mutation, CD79B mutation, interleukin 10/interleukin-6 (IL-10/IL-6) ratio, polymerase chain reaction (PCR) for monoclonal immunoglobulin heavy chain (IgH) and immunoglobulin kappa light chain (IgK) rearrangements, and imaging findings. The aggregated sensitivity of each diagnostic modality was reported and compared using the chi-squared (χ2) test. A total of 662 eyes from 29 retrospective studies reporting on patients diagnosed with PVRL were included. An IL-10/IL-6 ratio greater than 1 had the highest sensitivity (89.39%, n = 278/311 eyes, n = 16 studies) for PVRL, where the sensitivity was not significantly different when only vitreous samples were drawn (88.89%, n = 232/261 eyes, n = 13 studies) compared to aqueous samples (83.33%, n = 20/24, n = 2) (p = 0.42). Flow cytometry of vitreous samples gave a positive result in 66/75 eyes (88.00%, n = 6 studies) with PVRL, and monoclonal IgH rearrangements on PCR gave a positive result in 354/416 eyes (85.10%, n = 20 studies) with PVRL. MYD88 L265P and CD79B mutation analysis performed poorly, yielding a positive result in 63/90 eyes (70.00%, n = 8 studies) with PVRL, and 20/57 eyes (35.09%, n = 4 studies) with PVRL, respectively. Overall, our systematic review found that an IL-10/IL-6 ratio greater or equal to one may provide the highest sensitivity in identifying patients with PVRL. Future studies are needed to employ multiple diagnostic tools to aid in the detection of PVRL and to further establish nuanced guidelines when determining the optimal diagnostic tool to use in diverse patient populations.

CD79A work as a potential target for the prognosis of patients with OSCC: analysis of immune cell infiltration in oral squamous cell carcinoma based on the CIBERSORTx deconvolution algorithm.

OBJECTIVE: To analyze the abundance of infiltrating tumor immune cells in patients with oral squamous cell carcinoma (OSCC) and to search for potential targets that can predict patient prognosis. METHODS: A total of 400 samples from 210 patients with OSCC were collected using The Cancer Genome Atlas (TCGA) database. CIBERSORTx was used to evaluate the infiltration abundance of tumor immune cells. Potential target genes were searched to predict patient prognosis through case grouping, differential analysis, and enrichment analysis. Surgical excisional tissue sections of patients with oral squamous cell carcinoma admitted to the Department of Oral and Maxillofacial Surgery, Second Affiliated Hospital of Shantou University Medical College, from 2015 to 2018 were collected and followed up. RESULTS: The CIBERSORTx deconvolution algorithm was used to analyze the infiltration abundance of immune cells in the samples. Cases with a high infiltration abundance of naive and memory B lymphocytes improved the prognosis of OSCC patients. The prognosis of patients with low CD79A expression was significantly better than that of patients with high CD79A expression. CONCLUSION: CD79A can predict the infiltration abundance of B lymphocytes in the tumor microenvironment of patients with OSCC. CD79A is a potential target for predicting the prognosis of patients with OSCC. This study provides novel ideas for the treatment of OSCC and for predicting patient prognosis.

Mechanism of cystogenesis by Cd79a-driven, conditional mTOR activation in developing mouse nephrons.

Polycystic kidney disease (PKD) is a common genetic disorder arising from developmental and postnatal processes. Defects in primary cilia and their signaling (eg, mTOR) underlie the pathogenesis. However, how mTOR regulates tubular integrity remains unclear. The paucity of faithful models has limited our understanding of pathogenesis and, therefore, the refinement of therapeutic targets. To understand the role of mTOR in early cystogenesis, we studied an in-house mouse model, Cd79a-Cre;Tsc1ff. (Cd79a-Tsc1 KO hereafter), recapitulating human autosomal-dominant PKD histology. Cre-mediated Tsc1 depletion driven by the promoter for Cd79a, a known B-cell receptor, activated mTORC1 exclusively along the distal nephron from embryonic day 16 onward. Cysts appeared in the distal nephron at 1 weeks of age and mice developed definite PKD by 4 weeks. Cd79a-Tsc1 KO tubule cells proliferated at a rate comparable to controls after birth but continued to divide even after postnatal day 14 when tubulogenesis is normally completed. Apoptosis occurred only after 9 weeks. During postnatal days 7-11, pre-cystic Cd79a-Tsc1 KO tubule cells showed cilia elongation, aberrant cell intercalation, and mitotic division, suggesting that defective cell planar polarity (PCP) may underlie cystogenesis. mTORC1 was activated in a portion of cyst-lining cells and occasionally even when Tsc1 was not depleted, implying a non-autonomous mechanism. Our results indicate that mTORC1 overactivation in developing distal tubules impairs their postnatal narrowing by disrupting morphogenesis, which orients an actively proliferating cell toward the elongating axis. The interplay between mTOR and cilium signaling, which coordinate cell proliferation with PCP, may be essential for cystogenesis.

Prevalence and prognostic value of MYD88 and CD79B mutations in ocular adnexal large B-cell lymphoma: a reclassification of ocular adnexal large B-cell lymphoma.

AIMS: To (1) reclassify ocular adnexal large B-cell lymphomas (OA-LBCLs) per 2016 WHO lymphoma classification and (2) determine the prevalence of MYD88 and CD79B mutations and their association with clinical parameters among OA-LBCLs. METHODS: This study is a retrospective analysis of all OA-LBCLs diagnosed in Denmark between 1980 and 2018. Medical records and tissue samples were retrieved. Thirty-four OA-LBCLs were included. Fluorescence in situ hybridisation and Epstein-Barr-encoded RNA in situ hybridisation were used for the reclassification. Mutational status was established by allele-specific PCR and confirmed by Sanger sequencing. Primary endpoints were overall survival, disease-specific survival (DSS) and progression-free survival (PFS). RESULTS: Two LBCL subtypes were identified: diffuse large B-cell lymphoma (DLBCL) (27 of 32; 84%) and high-grade B-cell lymphoma (HGBL) with MYC and BCL2 and/or BCL6 rearrangements (5 of 32; 16%). cMYC/BCL2 double-expressor DLBCLs had a poorer DSS than non-double-expressor DLBCLs (5-year DSS, 25% vs 78%) (HR 0.23; 95% CI 0.06 to 0.85; p=0.014). MYD88 mutations were present in 10 (29%) of 34 lymphomas and carried a poorer PFS than wild-type cases (5-year PFS, 0% vs 43%) (HR 0.78; 95% CI 0.61 to 0.98; p=0.039). CD79B mutations were present in 3 (9%) of 34 cases. CONCLUSION: OA-LBCL consists mainly of two subtypes: DLBCL and HGBL with MYC and BCL2 and/or BCL6 rearrangements. MYD88 mutations are important drivers of OA-LBCL. MYD88 mutations, as well as cMYC/BCL2 double-expressor DLBCL, appear to be associated with a poor prognosis. Implementing MYD88 mutational analysis in routine diagnostics may improve OA-LBCL prognostication.

CD79B Y196 mutation is a potent predictive marker for favorable response to R-MPV in primary central nervous system lymphoma.

BACKGROUND: Rituximab, high-dose methotrexate (HD-MTX), procarbazine and vincristine (R-MPV), has significantly prolonged the survival of patients with primary central nervous system lymphoma (PCNSL), but predictive factors for response to R-MPV have not yet been investigated. Herein, we investigated the correlation of MYD88 L265P and CD79B Y196 mutations, which are the most frequently found molecular alterations in PCNSL, with prognosis of patients with PCNSL treated with R-MPV. METHODS: We investigated the long-term clinical course and status of MYD88 and CD79B genes in 85 patients with PCNSL treated with R-MPV or HD-MTX treatment, and the correlation of these genetic mutations with prognosis. RESULTS: R-MPV achieved an excellent tumor control rate (61.6% and 69.9% of 5-year progression-free and overall survival rates, respectively). While MYD88 L265P mutation had no significant effect on survival, patients with CD79B Y196 mutations exhibited prolonged survival (p < 0.05). However, the association of CD79B Y196 mutation with a better prognosis was not observed in the HD-MTX cohort, which indicated that CD79B Y196 mutation was a predictive marker for a favorable response to R-MPV. Furthermore, we established an all-in-one rapid genotyping system for these genetic mutations. CONCLUSIONS: In conclusion, CD79B Y196 mutation is a potent predictive marker for favorable response to R-MPV in PCNSL. The rapid identification of MYD88 L265P and CD79B Y196 mutations can be helpful not only for the accurate molecular diagnosis of PCNSL but also for the prediction of response to R-MPV.

Mechanism of CD79A and CD79B Support for IgM+ B Cell Fitness through B Cell Receptor Surface Expression.

The BCR consists of surface-bound Ig and a heterodimeric signaling unit comprised of CD79A and CD79B. Upon cognate Ag recognition, the receptor initiates important signals for B cell development and function. The receptor also conveys Ag-independent survival signals termed tonic signaling. Although the requirement of a CD79A/CD79B heterodimer for BCR complex assembly and surface expression is well established based on mice models, few studies have investigated this in human mature B cells. In this study, we found that human tonsillar B cells with high surface expression of IgM or IgG had potentiated BCR signaling compared with BCRlow cells, and high IgM expression in germinal center B cells was associated with reduced apoptosis. We explored the mechanism for IgM surface expression by CRISPR/Cas9-induced deletion of CD79A or CD79B in four B lymphoma cell lines. Deletion of either CD79 protein caused loss of surface IgM in all cell lines and reduced fitness in three. From two cell lines, we generated stable CD79A or CD79B knockout clones and demonstrated that loss of CD79A or CD79B caused a block in N-glycan maturation and accumulation of immature proteins, compatible with retention of BCR components in the endoplasmic reticulum. Rescue experiments with CD79B wild-type restored surface expression of CD79A and IgM with mature glycosylation, whereas a naturally occurring CD79B G137S mutant disrupting CD79A/CD79B heterodimerization did not. Our study highlights that CD79A and CD79B are required for surface IgM expression in human B cells and illuminates the importance of the IgM expression level for signaling and fitness.

The Prognostic Significance of CD79B Mutation in Diffuse Large B-Cell Lymphoma: A Meta-analysis and Systematic Literature Review.

INTRODUCTION: Previous studies have shown that diffuse large B-cell lymphoma (DLBCL) subtype with both B-cell antigen receptor complex-associated protein beta chain (CD79B) and myeloid differentiation primary response 88 mutations (MYD88) had inferior outcome under standard immunochemotherapy. However, the prognostic significance of CD79B alone in DLBCL has not been fully elucidated. We conducted a meta-analysis to investigate the role of CD79B mutation on overall survival (OS) in patients with DLBCL. METHODS: We performed literature search in PubMed and Embase databases and followed PRISMA guidelines to select publications for analysis. The primary and secondary outcome was OS and progression-free survival (PFS) respectively. Hazard ratio (HR) for OS/PFS in CD79B mutant group with that in wild-type group in R-chemotherapy patients was either estimated using Cox proportional hazard model from the studies with individual participant level data or extracted from the original publication with aggregated results. RESULTS: Nine eligible studies with survival information according to CD79B mutation status were included in this meta-analysis. The pooled hazard ratio for OS was 1.38 (95% CI, 1.13-1.70; p = 0.0021) for CD79B mutation, providing evidence that CD79B mutation was unfavorable prognostic factor for survival in DLBCL patients treated with immunochemotherapy. We identified the inferior prognostic impact of CD79B mutation was independent from well-established prognostic model in DLBCL, International Prognostic Index. The predictive power of CD79B mutation was stronger than that of MYD88 mutation. CONCLUSION: This meta-analysis revealed that CD79B mutation could be a key biomarker for DLBCL disease progression and future mechanism-based target therapy in DLBCL needs to be studied.

Unveiling the B cell receptor structure.

Molecular structures provide a road map for understanding and controlling B cell receptor activation.

Cryo-EM structures of two human B cell receptor isotypes.

The B cell receptor (BCR) complex plays a critical role in B cell development and immune responses. The assembly mechanisms underlying the BCR complex remain unknown. We determined the cryo-electron microscopy (cryo-EM) structures of human IgG-BCR and IgM-BCR, which consist of membrane-bound immunoglobulin molecules (mIg) and Igα/ß subunits at a 1:1 stoichiometry. Assembly of both BCR complexes involves their extracellular domains, membrane-proximal connection peptides, and transmembrane (TM) helices. The TM helices of mIgG and mIgM share a conserved set of hydrophobic and polar interactions with Igα/ß TM helices. By contrast, the IgG-Cγ3 and IgM-Cµ4 domains interact with extracellular Ig-like domains of Igα/ß through head-to-tail and side-by-side modes, respectively. This work reveals the structural basis for BCR assembly and provides insights into BCR triggering.

Cryo-EM structure of the human IgM B cell receptor.

The B cell receptor (BCR) initiates immune responses through antigen recognition. We report a 3.3-angstrom cryo-electron microscopy structure of human immunoglobulin M (IgM)-BCR in the resting state. IgM-BCR comprises two heavy chains, two light chains, and the Igα/Igß heterodimer. The ectodomains of the heavy chains closely stack against those of Igα/Igß, with one heavy chain locked between Igα and Igß in the juxtamembrane region. Extracellular interactions may determine isotype specificity of the BCR. The transmembrane helices of IgM-BCR form a four-helix bundle that appears to be conserved among all BCR isotypes. This structure contains 14 glycosylation sites on the IgM-BCR ectodomains and reveals three potential surface binding sites. Our work reveals the organizational principles of the BCR and may facilitate the design of antibody-based therapeutics.

United we stand: Double targeting of CD79B and CD20 in diffuse large B-cell lymphoma.

Polatuzumab vedotin is antibody-drug conjugate (ADC) targeting CD79B approved for the treatment of patients with relapsed/refractory diffuse large B-cell lymphoma when given in combination with bendamustine and rituximab. The report by Kawasaki et al. provide hints on what might be happening in lymphoma cells exposed to polatuzumab vedotin and to rituximab and on potential mechanism of resistance to the ADC. Commentary on: Kawasaki et al. The molecular rationale for the combination of polatuzumab vedotin plus rituximab in diffuse large B-cell lymphoma. Br J Haematol 2022;199:245-255.

Spatial transcriptome of a germinal center plasmablastic burst hints at MYD88/CD79B mutants-enriched diffuse large B-cell lymphomas.

The GC reaction results in the selection of B cells acquiring effector Ig secreting ability by progressing toward plasmablastic differentiation. This transition is associated with exclusion from the GC microenvironment. The aberrant expansion of plasmablastic elements within the GC fringes configures an atypical condition, the biological characteristics of which have not been defined yet. We investigated the in situ immunophenotypical and transcriptional characteristics of a nonclonal germinotropic expansion of plasmablastic elements (GEx) occurring in the tonsil of a young patient. Compared to neighboring GC and perifollicular regions, the GEx showed a distinctive signature featuring key regulators of plasmacytic differentiation, cytokine signaling, and cell metabolism. The GEx signature was tested in the setting of diffuse large B-cell lymphoma (DLBCL) as a prototypical model of lymphomagenesis encompassing transformation at different stages of GC and post-GC functional differentiation. The signature outlined DLBCL clusters with different immune microenvironment composition and enrichment in genetic subtypes. This report represents the first insight into the transcriptional features of a germinotropic plasmablastic burst, shedding light into the molecular hallmarks of B cells undergoing plasmablastic differentiation and aberrant expansion within the noncanonical setting of the GC microenvironment.