The human cathelicidin peptide LL-37 induces autophagy in human macrophages. Different post-translational modifications (PTMs) such as citrullination, acetylation, and formylation impact LL-37, yet their effect on autophagy remains unknown. Thus, we set out to study how the cellular source could impact PTM of LL-37 and subsequent effects on autophagy initiation. Neutrophil-released LL-37 failed to induce autophagy, unlike macrophage-released LL-37. Mass spectrometry analysis revealed modifications on neutrophil-derived LL-37, especially at the N terminus, while macrophage-derived LL-37 remained mostly native. Native LL-37 initiated autophagy, while formylated and acetylated versions did not. Truncated peptides lacking the N-terminal di-leucine motif or substituted with di-alanine did not initiate autophagy. Native LL-37 failed to initiate autophagy in macrophages with genetic inactivation of dipeptidyl peptidase-1. An intact N-terminal di-leucine motif in LL-37 was crucial for autophagy initiation, and modifications abrogated the effects. This pathway presents a novel way to regulate the effects of LL-37 in infection or inflammation.

Splice-switching oligonucleotides (SSOs) have been developed as a treatment for various disorders, including Duchenne muscular dystrophy and spinal muscular atrophy. Here, the activity of several different SSOs was investigated as potential treatments for B lymphocyte disorders with a focus on X-linked agammaglobulinemia (XLA), caused by defects in the gene encoding Bruton's tyrosine kinase (BTK). In this study, the activity of locked nucleic acid (LNA), tricyclo-DNA (tcDNA), phosphoryl guanidine oligonucleotides (PGO) and phosphorodiamidate morpholino oligomers (PMO) were compared, targeting the pseudoexon region of BTK pre-mRNA. We further investigated the effect of conjugating cell-penetrating peptides, including Pip6a, to the SSOs. The effect was measured as splice-switching in vitro as well as in a further developed, bacterial artificial chromosome transgenic mouse model of XLA. Therapy in the form of intravenous infusions 2 times a week during 3 weeks of PMO oligomers conjugated to Pip6a was sufficient to partly restore the in vivo B lineage phenotype. SSOs treatment also provides a unique opportunity to get insights into a restoration process, when B lymphocytes of different maturation stages are simultaneously splice-corrected.

Whilst the broad clonal architecture of naturally progressing chronic lymphocytic leukemia (CLL) has been described, a comprehensive picture of how chemotherapy and targeted agents reshape that landscape is lacking. Here we integrate clone-specific growth kinetics with mutational profiles, transcriptomic subtypes, and CpG-methylation-based epigenetic classes to capture the multidimensional evolutionary responses of CLL under native conditions and during treatment. We previously reported a systematic whole-exome sequencing (WES) analysis of 417 leukemia–germline pairs from 169 treatment-naïve patients ≥ 65 y (Karisani et al., Blood 2024). The treatment arm comprised 83 patients who received ibrutinib and 39 who received chlorambucil in the RESONATE-2 trial (NCT01722487). Forty-seven age-matched “watch-and-wait” patients from the CLL Research Consortium served as untreated controls. Peripheral-blood samples were collected at baseline and again ~300 d and ~600 d after therapy initiation (or diagnosis in the watch-and-wait cohort), enabling longitudinal clonal tracking. WES data were processed with PhylogicNDT to reconstruct clonal architectures, define phylogenies, and identify significant clonal shifts. MutSig tools identified mutations enriched in expanding or contracting clones. Pretreatment RNA-sequencing profiles were grouped into transcriptional subtypes by consensus clustering based on the Louvain algorithm. Differentially methylated regions plus epitypes were called from reduced representation bisulfite sequencing data. Across the 169 patients with WES, we resolved 579 subclonal clusters. Significant clonal shifts (defined as a distribution shift of cancer cell fraction in a subclone of >95% between two timepoints) were uncommon during watch-and-wait (36%) but markedly higher after therapy — chlorambucil 67% (q = 0.01), and ibrutinib 77% (q < 10-4). In ibrutinib-treated CLL, regressing subclones were enriched for KRAS (q<10-3) and SF3B1 mutations (q<10-3), whereas expanding subclones preferentially harboured mutations in BIRC3 (q<10-4), NOTCH1 (q <10-3), TP53 (q=0.02), and POT1 (q=0.098). In chlorambucil-treated patients, no specific mutations were found to be enriched in expanding or regressing subclones. Using the recently defined CLL expression clusters (ECs) in patients treated with chemoimmunotherapy as defined by Knisbacher et al. (Nat Genet 2022), we were unable to identify any relationship between ECs and outcomes. We therefore sought to identify de novo ECs with prognostic relevance in the context of BTK-inhibition (BTKi-ECs). We identified a transcriptionally defined patient subgroup (C4, n=20) associated with inferior progression-free survival (median PFS = 63 months, log-rank q=0.05), independent of known prognostic clinical and molecular features, including epitypes, in multivariate analysis (Cox HR=3.7, 95% CI: 1.6-8.6, q=0.02). Gene-set enrichment in this cluster highlighted TNF-ɑ signalling via NF-κB (REL, TNFAIP3, NFKB2) and G2M checkpoint pathways (SMC4, EZH2). We also identified a distinct transcriptionally defined patient subgroup (C3, n=18) that was enriched for patients harboring at least one contracting subclone and no expanding subclones (q=0.005). This cluster showed a relative depletion of mutations within the chromatin modification pathway (6% vs 50%, q<0.01). Gene-set enrichment in this cluster highlighted a downregulation of genes in the TNF-ɑ signalling via NF-κB pathway (SOCS3, ICOSLG, NFKB2). BTK inhibition and chemotherapy drive distinct evolutionary trajectories in CLL. Multi-omics profiling reveals mutation-defined subclones with divergent sensitivity to targeted therapy and delineates two informative expression states: a high-risk NF-κB/inflammatory cluster (C4; poor PFS) and a cluster enriched with contracting subclones with depleted TNF-ɑ signalling via NF-κB (C3). Integrating clonal growth kinetics with genomic, transcriptomic, and methylation data can potentially identify patients likely to progress on BTK inhibitors and identify actionable pathways for adaptive or combination therapy.

Single-cell whole genome sequencing (scWGS) enables detailed analysis of genomic heterogeneity at the cellular level. Comprehensive characterization of the cell genome requires whole genome amplification (WGA). Here, we systematically compared two WGA technologies, Multiple Displacement Amplification (MDA) and Primary Template-directed Amplification (PTA), commercially available in the Qiagen REPLI-g kit and BioSkryb ResolveDNA kit, respectively. BioSkryb PTA sequencing libraries consistently outperformed Qiagen MDA across most quality metrics, including genome coverage breadth and uniformity. In copy number variation (CNV) detection, PTA calls showed higher accuracy and sensitivity, including reliable detection of small CNVs at low sequencing depth. Furthermore, SNP array genotyping of the same WGA products confirmed the findings from sequencing while also providing allelic information. Moreover, BioSkryb PTA CNV detection from SNP arrays matched the performance of low-pass sequencing, supporting its utility as an alternative for WGA quality control and single-cell CNV profiling. Overall, BioSkryb PTA kit demonstrated superior performance over Qiagen MDA kit for single cell genome analysis. ### Competing Interest Statement The authors have declared no competing interest. Swedish Research Council, https://ror.org/03zttf063 SciLifeLab Knut and Alice Wallenberg Foundation, https://ror.org/004hzzk67 ALF funding from Region Uppsala Swedish Blood Cancer Association Swedish Cancer Society, https://ror.org/0527jb766 Radiumhemmets forskningsfonder

Age is a risk factor for hematologic malignancies. Attributes of the aging hematopoietic system include increased myelopoiesis, impaired adaptive immunity, and a functional decline of the hematopoietic stem cells (HSCs) that maintain hematopoiesis. Changes in the composition of diverse HSC subsets have been suggested to be responsible for age-related alterations, however, the underlying regulatory mechanisms are incompletely understood in the context of HSC heterogeneity. In this study, we investigated how distinct HSC subsets, separated by CD49b, functionally and molecularly change their behavior with age. We demonstrate that the lineage differentiation of both lymphoid-biased and myeloid-biased HSC subsets progressively shifts to a higher myeloid cellular output during aging. In parallel, we show that HSCs selectively undergo age-dependent gene expression and gene regulatory changes in a progressive manner, which is initiated already in the juvenile stage. Overall, our studies suggest that aging intrinsically alters both cellular and molecular properties of HSCs. Aging is a risk factor for blood malignancies, leading to increased myelopoiesis and impaired immunity. Here, the authors show that aging alters cellular and molecular properties of HSC subsets, with changes starting as early as the juvenile stage.

Background: In an academic clinical trial, we are investigating an alternative strategy for ibrutinib dosing in patients with chronic lymphocytic leukemia (CLL) who have received at least 6 months (mo) of therapy and are in stable partial remission (PR). Briefly, treatment is suspended and patients followed off therapy until early signs of progressive disease (PD), at which ibrutinib is re-instituted. Such ‘ON-OFF’ ibrutinib cycles are repeated until resistance and need of alternative therapy. In the phase 1b part of the study, we showed that ibrutinib can safely be suspended (Lundin et al., 2021). A spin-off study runs in parallel with the trial to characterize the cellular and molecular changes induced by this alternative dosing of ibrutinib. Methods. Peripheral blood (PB) samples were collected from 20 patients right before the first treatment interruption (i.e. start of OFF-phase) and at 2 weeks, 1 mo, 3 mo, 6 mo and 12 mo after treatment interruption and before re-start. Pre-treatment samples (i.e. at primary start of ibrutinib) were also available for 11/20 patients while samples taken before re-start of treatment (i.e. start of ON-phase) were available for 10/20 patients. Flow cytometry analysis of the different T- and NK-cells subsets was performed and plasma inflammation-related biomarkers were assessed by a proximity extension assay. Quantitative digital-droplet PCR is ongoing to detect the occurrence of mutations within BTK and PLCG2 on samples taken before treatment stop and at re-start. Results: After treatment interruption, CLL cells remained stable until time for re-start when they increased (p<0.0005). The same dynamics were observed for CD8+ and CD4+ cells (p=0.03 and p=0.01, respectively) and for Th1 and Th2 cells (p=0.001, respectively). Naïve CD4+ T cells (CCR7+CD45RA+) remained stable throughout the OFF phase until re-start. CD4+ central memory (CM) T cells (CCR7+CD45RA-) started increasing at mo 6 (p=0.03) and were still higher at re-start (p=0.007). Effector memory (EM) CD4+ T cells (CCR7-CD45RA-) remained stable until re-start (p=0.03). CD4+ T effector memory re-expressing CD45RA (TEMRA; CCR7-CD45RA+) decreased at mo 3 after stop (p=0.01) until mo 12 (p=0.004) but increased again at re-start. Remarkably, regulatory T cells (Tregs) started increasing earlier compared to the other cell populations, from 3 mo (p= 0.02) and progressively more significantly until re-start (p= 0.001). NK cells decreased initially (p= 0.04 at wk 2) and later increased from 12 mo to restart (p=0.003). The expression of all exhaustion markers on T cells increased at re-start: CD4+PD-1+ (p=0.005), CD8+PD-1+ (p=0.002), CTLA-4+CD4+ (p=0.005), CTLA-4+CD8+ (p=0.02), TIGIT+CD4+ (p=0.002), TIGIT+CD8+ (p=0.002). When analyzing 92 inflammatory plasma protein biomarkers, we observed the following patterns: 1) some markers which had decreased during treatment, increased again in the OFF-phase, such as CCL3 and CCL4; 2) some markers which had increased during ibrutinib treatment, significantly decreased in the OFF-phase, such as AREG, TNFSF13, EDAR, CST5; 3) some markers which had decreased during treatment, stayed at low levels in the OFF-phase, such as VIM, NT3, NF2, IRAK4, BACH1 and FGF2. The markers in the first group were the majority. Changes were considered statistically significant when the adjusted p-value was <0.05. Conclusions. After interruption of ibrutinib, the immune cell phenotype achieved after long-term treatment seems to remain substantially stable until PD occurs, at which the phenotype reverts to the pre-treatment one.Similarly, the majority of the changes in plasma protein biomarkers acquired with treatment gradually revert to the pre-treatment status. However, a minority of them remained unchanged despite PD, for reasons to be investigated.

Bruton 's tyrosine kinase (BTK) is an enzyme needed for B -cell survival, and its inhibitors have become potent targeted medicines for the treatment of B -cell malignancies. The initial activation event of cytoplasmic protein -tyrosine kinases is the phosphorylation of a conserved regulatory tyrosine in the catalytic domain, which in BTK is represented by tyrosine 551. In addition, the tyrosine 223 (Y223) residue in the SRC homology 3 (SH3) domain has, for more than 2 decades, generally been considered necessary for full enzymatic activity. The initial recognition of its potential importance stems from transformation assays using nonlymphoid cells. To determine the biological signi ficance of this residue, we generated CRISPR-Cas -mediated knockin mice carrying a tyrosine to phenylalanine substitution (Y223F), maintaining aromaticity and bulkiness while prohibiting phosphorylation. Using a battery of assays to study leukocyte subsets and the morphology of lymphoid organs, as well as the humoral immune responses, we were unable to detect any difference between wild -type mice and the Y223F mutant. Mice resistant to irreversible BTK inhibitors, through a cysteine 481 to serine substitution (C481S), served as an additional immunization control and mounted similar humoral immune responses as Y223F and wild -type animals. Collectively, our findings suggest that phosphorylation of Y223 serves as a useful proxy for phosphorylation of phospholipase C gamma 2 (PLCG2), the endogenous substrate of BTK. However, in contrast to a frequently held conception, this posttranslational modi fication is dispensable for the function of BTK.

Abstract Background RNA sequencing has become the mainstay for studies of gene expression. Still, analysis of rare cells with random hexamer priming – to allow analysis of a broader range of transcripts – remains challenging. Results We here describe a tagmentation-based, rRNA blocked, random hexamer primed RNAseq approach (T-RHEX-RNAseq) for generating stranded RNAseq libraries from very low numbers of FACS sorted cells without RNA purification steps. Conclusion T-RHEX-RNAseq provides an easy-to-use, time efficient and automation compatible method for generating stranded RNAseq libraries from rare cells.

The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-ɣ and CXCL10 were downregulated. The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Cohesin is a major structural component of mammalian genomes and is required to maintain loop structures. While acute depletion in short-term culture models suggests a limited importance of cohesin for steady-state transcriptional circuits, long-term studies are hampered by essential functions of cohesin during replication. Here, we study genome architecture in a postmitotic differentiation setting, the differentiation of human blood monocytes (MO). We profile and compare epigenetic, transcriptome and 3D conformation landscapes during MO differentiation (either into dendritic cells or macrophages) across the genome and detect numerous architectural changes, ranging from higher level compartments down to chromatin loops. Changes in loop structures correlate with cohesin-binding, as well as epigenetic and transcriptional changes during differentiation. Functional studies show that the siRNA-mediated depletion of cohesin (and to a lesser extent also CTCF) markedly disturbs loop structures and dysregulates genes and enhancers that are primarily regulated during normal MO differentiation. In addition, gene activation programs in cohesin-depleted MO-derived macrophages are disturbed. Our findings implicate an essential function of cohesin in controlling long-term, differentiation- and activation-associated gene expression programs.

Multiple myeloma (MM) is an incurable and aggressive plasma cell malignancy characterized by a complex karyotype with multiple structural variants (SVs) and copy-number variations (CNVs). Linked-read whole-genome sequencing (lrWGS) allows for refined detection and reconstruction of SVs by providing long-range genetic information from standard short-read sequencing. This makes lrWGS an attractive solution for capturing the full genomic complexity of MM. Here we show that high-quality lrWGS data can be generated from low numbers of cells subjected to fluorescence-activated cell sorting (FACS) without DNA purification. Using this protocol, we analyzed MM cells after FACS from 37 patients with MM using lrWGS. We found high concordance between lrWGS and fluorescence in situ hybridization (FISH) for the detection of recurrent translocations and CNVs. Outside of the regions investigated by FISH, we identified >150 additional SVs and CNVs across the cohort. Analysis of the lrWGS data allowed for resolution of the structure of diverse SVs affecting the MYC and t(11;14) loci, causing the duplication of genes and gene regulatory elements. In addition, we identified private SVs causing the dysregulation of genes recurrently involved in translocations with the IGH locus and show that these can alter the molecular classification of MM. Overall, we conclude that lrWGS allows for the detection of aberrations critical for MM prognostics and provides a feasible route for providing comprehensive genetics. Implementing lrWGS could provide more accurate clinical prognostics, facilitate genomic medicine initiatives, and greatly improve the stratification of patients included in clinical trials.

The development of B cells relies on an intricate network of transcription factors critical for developmental progression and lineage commitment. In the B cell developmental trajectory, a temporal switch from predominant Foxo3 to Foxo1 expression occurs at the CLP stage. Utilizing VAV-iCre mediated conditional deletion, we found that the loss of FOXO3 impaired B cell development from LMPP down to B cell precursors, while the loss of FOXO1 impaired B cell commitment and resulted in a complete developmental block at the CD25 negative proB cell stage. Strikingly, the combined loss of FOXO1 and FOXO3 resulted in the failure to restrict the myeloid potential of CLPs and the complete loss of the B cell lineage. This is underpinned by the failure to enforce the early B-lineage gene regulatory circuitry upon a predominantly pre-established open chromatin landscape. Altogether, this demonstrates that FOXO3 and FOXO1 cooperatively govern early lineage restriction and initiation of B-lineage commitment in CLPs.

The value of genome-wide over targeted driver analyses for predicting clinical outcomes of cancer patients is debated. Here, we report the whole-genome sequencing of 485 chronic lymphocytic leukemia patients enrolled in clinical trials as part of the United Kingdom’s 100,000 Genomes Project. We identify an extended catalog of recurrent coding and noncoding genetic mutations that represents a source for future studies and provide the most complete high-resolution map of structural variants, copy number changes and global genome features including telomere length, mutational signatures and genomic complexity. We demonstrate the relationship of these features with clinical outcome and show that integration of 186 distinct recurrent genomic alterations defines five genomic subgroups that associate with response to therapy, refining conventional outcome prediction. While requiring independent validation, our findings highlight the potential of whole-genome sequencing to inform future risk stratification in chronic lymphocytic leukemia.

Natural killer (NK) cells play roles in viral clearance and early surveillance against malignant transformation, yet our knowledge of the underlying mechanisms controlling their development and functions remain incomplete. To reveal cell fate-determining pathways in NK cell progenitors (NKP), we utilized an unbiased approach and generated comprehensive gene expression profiles of NK cell progenitors. We found that the NK cell program was gradually established in the CLP to preNKP and preNKP to rNKP transitions. In line with FOXO1 and FOXO3 being co-expressed through the NK developmental trajectory, the loss of both perturbed the establishment of the NK cell program and caused stalling in both NK cell development and maturation. In addition, we found that the combined loss of FOXO1 and FOXO3 caused specific changes to the composition of the non-cytotoxic innate lymphoid cell (ILC) subsets in bone marrow, spleen, and thymus. By combining transcriptome and chromatin profiling, we revealed that FOXO TFs ensure proper NK cell development at various lineage-commitment stages through orchestrating distinct molecular mechanisms. Combined FOXO1 and FOXO3 deficiency in common and innate lymphoid cell progenitors resulted in reduced expression of genes associated with NK cell development including ETS-1 and their downstream target genes. Lastly, we found that FOXO1 and FOXO3 controlled the survival of committed NK cells via gene regulation of IL-15Rβ (CD122) on rNKPs and bone marrow NK cells. Overall, we revealed that FOXO1 and FOXO3 function in a coordinated manner to regulate essential developmental genes at multiple stages during murine NK cell and ILC lineage commitment.

Few approaches have been made toward exploring autologous NK cells in settings of cancer immunotherapy. Here, we demonstrate the feasibility of infusing multiple doses of ex vivo activated and expanded autologous NK cells in patients with multiple myeloma (MM) post-autologous stem cell transplantation. Infused NK cells were detected in circulation up to 4 weeks after the last infusion. Elevations in plasma granzyme B levels were observed following each consecutive NK cell infusion. Moreover, increased granzyme B levels were detected in bone marrow 4 weeks after the last infusion. All measurable patients had objective, detectable responses after NK cell infusions in terms of reduction in M-component and/or minimal residual disease. The present study demonstrates that autologous NK cell-based immunotherapy is feasible in a setting of MM consolidation therapy. It opens up the possibility for usage of autologous NK cells in clinical settings where patients are not readily eligible for allogeneic NK cell-based immunotherapies.

Hematopoiesis is maintained by functionally diverse lineage-biased hematopoietic stem cells (HSCs). The functional significance of HSC heterogeneity and the regulatory mechanisms underlying lineage bias are not well understood. However, absolute purification of HSC subtypes with a pre-determined behavior remains challenging, highlighting the importance of continued efforts toward prospective isolation of homogeneous HSC subsets. In this study, we demonstrate that CD49b subdivides the most primitive HSC compartment into functionally distinct subtypes: CD49b(-) HSCs are highly enriched for myeloid-biased and the most durable cells, while CD49b(+) HSCs are enriched for multipotent cells with lymphoid bias and reduced self-renewal ability. We further demonstrate considerable transcriptional similarities between CD49b(-) and CD49b(+) HSCs but distinct differences in chromatin accessibility. Our studies highlight the diversity of HSC functional behaviors and provide insights into the molecular regulation of HSC heterogeneity through transcriptional and epigenetic mechanisms.

Background: In classical Hodgkin lymphoma (cHL) the malignant cells represent only a small fraction of the tumor mass. Yet, they orchestrate a lymphocyte-dominated tumor microenvironment (TME) that supports their survival and growth. The systemic effects of this local immunomodulation are not fully elucidated. In this study, we aimed at characterising circulating lymphocytes and plasma proteins in cHL patients in relation to clinical parameters and treatment effect. Methods: Peripheral blood (PB) samples were obtained from 48 consecutive patients at diagnosis (baseline, BL) and at 2 time points after primary treatment, right at the end of treatment (EoT) and at follow-up 6 months after EoT (FU). Twenty-eight patients had limited-stage (I-IIA) and 20 had advanced-stage (IIB-IV) disease. All the patients in the FU analysis were in complete remission. Twenty healthy individuals were included as controls. Cells from PB and LN were freshly analysed by flow cytometry, and plasma proteins by proximity extension assay (PEA). Concentrations of CCL17/TARC in plasma were also measured by Enzyme-Linked ImmunoSorbent Assay. Results: At BL, the numbers of B cells were lower in both limited- and advanced-stage cHL compared to controls, while T cells were normal. Advanced-stage patients had fewer NK cells with a functionally impaired phenotype. Compared to controls, cHL patients had higher frequencies of proliferating T cells as well as higher expression of programmed death (PD)-1 and cytotoxic T lymphocyte antigen (CTLA)-4 in circulating T cells, and lower naïve T-cell frequencies. The plasma concentration of CCL17/TARC was elevated in both limited- and advanced-stage cHL compared to controls. The frequencies of T and B cells positively correlated between the PB and LN compartments. Distinct immune cellular and plasma protein biomarker profiles were observed in patients with a high tumor burden (i.e. bulky tumor and/or >2 nodal sites involved and/or stage IV) and those with high inflammation (i.e. ESR ≥50). T-cell exhaustion and NK-cell depletion were reversed by standard first-line treatment and CCL17/TARC concentrations also dropped back to control levels. Patients who received radiotherapy involving the mediastinum had low T-cell counts for a prolonged period. Conclusion: The immunomodulation of lymphocytes in the TME of cHL might affect immune biomarkers in the PB. Most immunological changes are reverted after successful standard primary treatment.

In classical Hodgkin lymphoma (cHL), the malignant cells represent only a small fraction of the tumor. Yet, they orchestrate a lymphocyte-dominated tumor microenvironment (TME) that supports their survival and growth. The systemic effects of this local immunomodulation are not fully elucidated. Here, we aimed at characterizing circulating lymphocytes and plasma proteins in relation to clinical parameters and treatment effect. Peripheral blood (PB) samples were obtained from 48 consecutive patients at diagnosis and at 2 time points after successful primary treatment. Single-cell suspensions were prepared from lymph node (LN) biopsies obtained for routine diagnostic purposes. Twenty healthy individuals were included as controls. Cells from PB and LN were analyzed by flow cytometry, and plasma proteins by Proximity Extension Assay. We found that the frequencies of T and B cells positively correlated between the LN and the PB compartments. Compared to controls, cHL patients had higher frequencies of proliferating T cells as well as higher expression of programmed death (PD)-1 and cytotoxic T lymphocyte antigen (CTLA)-4 in circulating T cells, and lower naive T-cell frequencies. Advanced-stage patients had fewer NK cells with a functionally impaired phenotype. Differences in the immune profile were observed in patients with a high tumor burden and with high inflammation, respectively. Most of these deviations disappeared after standard first-line treatment. Patients who received radiotherapy involving the mediastinum had low T-cell counts for a prolonged period. Our findings suggest that the immunomodulation of lymphocytes in the TME of cHL might affect immune biomarkers in the PB.

The generation of high-affinity antibodies against pathogens and vaccines requires the germinal center (GC) reaction, which relies on a complex interplay between specialized effector B and CD4 T lymphocytes, the GC B cells and T follicular helper (TFH) cells. Intriguingly, several positive key regulators of the GC reaction are common for both cell types. Here, we report that the transcription factor Bhlhe40 is a crucial cell-intrinsic negative regulator affecting both the B and T cell sides of the GC reaction. In activated CD4 T cells, Bhlhe40 was required to restrain proliferation, thus limiting the number of TFH cells. In B cells, Bhlhe40 executed its function in the first days after immunization by selectively restricting the generation of the earliest GC B cells but not of early memory B cells or plasmablasts. Bhlhe40-deficient mice with progressing age succumbed to a B cell lymphoma characterized by the accumulation of monoclonal GC B-like cells and polyclonal TFH cells in various tissues.