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The molecular causes of myeloproliferative neoplasms (MPNs) have not yet been fully elucidated. Approximately 7% to 8% of the patients carry predisposing genetic germline variants that lead to driver mutations, which enhance JAK-STAT signaling. To identify additional predisposing genetic germline variants, we performed whole-exome sequencing in 5 families, each with parent-child or sibling pairs affected by MPNs and carrying the somatic JAK2 V617F mutation. In 4 families, we detected rare germline variants in known tumor predisposition genes of the DNA repair pathway, including the highly penetrant BRCA1 and BRCA2 genes. The identification of an underlying hereditary tumor predisposition is of major relevance for the individual patients as well as for their families in the context of therapeutic options and preventive care. Two patients with essential thrombocythemia or polycythemia vera experienced progression to acute myeloid leukemia, which may suggest a high risk of leukemic transformation in these familial MPNs. Our study demonstrates the relevance of genetic germline diagnostics in elucidating the causes of MPNs and suggests novel therapeutic options (eg, PARP inhibitors) in MPNs. Furthermore, we uncover a broader tumor spectrum upon the detection of a germline mutation in genes of the DNA repair pathway.

Classical CD14+monocytes are the predominant monocyte population in human blood. They are primarily engaged in host defense programs and secrete pro-inflammatory cytokines that orchestrate immune responses. While aberrant monocyte activity elicits cytokine storms, dysfunctional monocytes are associated with immunoparalysis, an equally life-threatening state of immunosuppression observed in severe sepsis, trauma, or respiratory viral infections. Hence, unraveling the mechanisms controlling monocyte functions is paramount in diverse clinical settings. Here, we reveal a critical dependency on platelets for the pro-inflammatory cytokine responses of human monocytes. We found that platelet removal from freshly isolated primary human monocytes causes monocyte immunoparalysis, characterized by transcriptional shut down of pro-inflammatory genes, and impaired cytokine secretion upon Toll-like and NOD-like receptor activation. Notably, anergic platelet-depleted monocytes can be reactivated upon their replenishment with autologous platelets. Moreover, monocytes from patients with immune thrombocytopenia display naturally impaired cytokine responses, which were also reversed by platelet supplementation. Mechanistically, we show that the platelet-monocyte crosstalk regulating monocyte cytokine responses is independent of classical co-stimulatory molecules, integrins, CCL5, CXCL12, Siglec-7, and Sialic Acids, and involves the trans-cellular propagation of platelet p38 MAPK signaling through platelet vesicles. Our findings delineate platelets as paramount regulators of monocyte innate immune functions.Key PointsPlatelets are essential to TLR and NLR cytokine responses of human monocytes,Platelet depletion causes a dynamic and reversible transcriptional reprogramming of human monocytes;Platelet supplementation reverts monocyte immunoparalysis in immune thrombocytopenia;Platelets are cellular sources of active transcription factors;Platelet supply p38 MAPK that reactivate cytokine responses in p38-inhibited monocytes.

Annals of hematology 100(1), 97-104 (2021). doi:10.1007/s00277-020-04304-Y, Published by Springer, Berlin ; Heidelberg ; New York

British journal of haematology : BJHaem 200(5), 643-651 (2022). doi:10.1111/bjh.18563, Published by Wiley-Blackwell, Oxford [u.a.]

Kessler et al. identify aberrant DNA recognition by cGAS/STING and IFN-I production by inflammatory macrophages as a driver of severe ANCA-associated vasculitis. Pharmacological interventions blocking this pathway ameliorate disease and accelerate recovery, identifying potential targets for therapeutic intervention in patients., Autoimmune vasculitis is a group of life-threatening diseases, whose underlying pathogenic mechanisms are incompletely understood, hampering development of targeted therapies. Here, we demonstrate that patients suffering from anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) showed increased levels of cGAMP and enhanced IFN-I signature. To identify disease mechanisms and potential therapeutic targets, we developed a mouse model for pulmonary AAV that mimics severe disease in patients. Immunogenic DNA accumulated during disease onset, triggering cGAS/STING/IRF3-dependent IFN-I release that promoted endothelial damage, pulmonary hemorrhages, and lung dysfunction. Macrophage subsets played dichotomic roles in disease. While recruited monocyte-derived macrophages were major disease drivers by producing most IFN-beta, resident alveolar macrophages contributed to tissue homeostasis by clearing red blood cells and limiting infiltration of IFN-beta-producing macrophages. Moreover, pharmacological inhibition of STING, IFNAR-I, or its downstream JAK/STAT signaling reduced disease severity and accelerated recovery. Our study unveils the importance of STING/IFN-I axis in promoting pulmonary AAV progression and identifies cellular and molecular targets to ameliorate disease outcomes.

Trials 22(1), 765 (2021). doi:10.1186/s13063-021-05703-w, Published by BioMed Central, London

Introduction: The licenced starting dose of bosutinib is 400 mg QD for first line therapy and 500 mg QD in later lines in CML. Gastrointestinal (GI) adverse events (AE) are observed in up to 90% in similar patient cohorts (BYOND, Hochhaus et al; Leukemia 2020). The goal of this study was to evaluate whether a bosutinib step-in dosing regimen decreases GI toxicity while maintaining optimal efficacy in patients (pts) with CML after failure or intolerance to 2G-TKIs. Methods: This is the first and final analysis of the BODO "Bosutinib Dose Optimization Study" trial (NCT02577926), which is a multicenter, open-label single arm phase II study testing tolerability and efficacy of 2 nd& 3 rd line bosutinib step-in dosing in chronic phase CML pts intolerant and/or refractory to previous imatinib, and/or nilotinib, and/or dasatinib therapy. Bosutinib was commenced with 300 mg QD and was (in the absence of >G1 toxicities) dose-increased by increments of 100 mg daily dosing every 14 days if applicable up to a maximum dose of 500 mg QD. The primary endpoint (PE) was the incidence of grade 2 to 4 GI toxicity AEs within 6 months after registration. 127 pts were planned to be recruited. However, due to slow recruitment, the trial had to be stopped prematurely after inclusion of 57 pts. The 95% confidence interval (CI) around the estimated rate of the PE was calculated in accordance with Clopper and Pearson. Results: Pts´ characteristics are presented in Table 1. 23 (40.4%) pts were intolerant, 20 resistant (35.1%), and 14 (24.6%) both intolerant and resistant to previous TKI treatment. 20 (35.1%) pts entered the study in molecular response (at least MMR at screening). The probability of MMR after 24 months of treatment was 79% (95% CI: 65.8% to 87.5%); probabilities of MMR, MR4, MR4.5 are shown in Figure 1. Six out of 7 intolerant pts without MMR at baseline reached MMR or better molecular response with bosutinib. Thirty pts were refractory to previous therapy (19 being resistant; 11 being resistant and intolerant) lacking baseline MMR, of which 19 pts achieved MMR or better (2 pts with MR4.5, 2 with MR4 and 15 with MMR). Eight out of 30 pts did not achieve MMR and 3 experienced complications (2 pts with SAEs that led to discontinuation and 1 death). No patient progressed to accelerated/blast phase on treatment. Two pts died (1 CML progression (no MMR with bosutinib, death 6 months after allogenic stem cell transplant); 1 cerebral cavernoma unrelated to bosutinib). In the overall patient population (N = 57), all pts had ≥1 any grade TEAE and 71.9% of patients had ≥1 grade 3/4 TEAE. SAEs occurred in 28.1% of pts. A total of 949 AEs were reported during the study. The most frequently reported AEs (SOC terms) were GI disorders (n=346, 36.5%) and investigations (n=206, 21.7%). Among the GI events (n=346) diarrhea (55.5%), nausea (16.2%) and abdominal pain (9.8%) were most common; among investigations (n=206) liver enzyme increases were most frequent (ALT increase (26.7%), AST increase 17%). The PE was evaluated for 50 out of 57 pts (4 pts with treatment < 14 days + 3 pts with observation < 6 months were excluded from the analysis). Twenty pts did not develop any clinically relevant GI-toxicity during the first 6 months. Thus, the rate of GI-toxicity (grade 2 to 4) within the first 6 months of treatment was 60.0% (95% confidence interval: 45.2% to 73.6%), accordingly, the alternative hypothesis of the trial (GI-toxicity was assumed to be less than 40%) could not be accepted. However, only in 1 patient GI-toxicity led to discontinuation. Twenty-five pts discontinued bosutinib prematurely (17 due to AEs; 5 with insufficient response; 3 with other reasons). Conclusion: This is 1 of the largest cohorts published on the efficacy and safety of bosutinib after intolerance/failure to first-line 2G-TKIs. Given the limitations of a single-arm study with incomplete recruitment, we could not demonstrate an advantage of the step-in dosing concept chosen here to reduce the frequency of grade 2-4 GI toxicity overall. However, using this regimen, bosutinib was able to induce optimal responses in almost two thirds of pts previously resistant to 2G-TKIs while GI toxicity rarely led to treatment discontinuation. We conclude that treatment with bosutinib is safe (rates of AEs being similar to other trials (e.g. BYOND)) and efficacious as 2 nd and 3 rd line therapy after failure of previous 2G-TKI therapy whereas an advantage of run-in dosing regimens remains to be proven. Figure 1 Figure 1. Disclosures Isfort: Mundipharma: Other: Travel reimbursement; Amgen: Other: Travel reimbursement; Roche: Other: Travel reimbursement; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Hexal: Other: Travel reimbursement; Alexion: Other: Travel reimbursement; BMS: Honoraria; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement. Wolf: Roche: Honoraria, Research Funding; MSD: Honoraria, Research Funding; BMS-Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Takeda: Honoraria; Gilead: Honoraria; Incyte: Honoraria; GEMOAB: Honoraria. Teichmann: Pfizer: Membership on an entity's Board of Directors or advisory committees. Crysandt: Incyte: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees. Burchert: Novartis: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding; Pfizer: Honoraria; Incyte: Honoraria; Gilead: Honoraria; BMS: Honoraria. Hochhaus: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Incyte: Research Funding. Saussele: Pfizer: Honoraria; Incyte: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Roche: Honoraria. Kiani: Novartis Pharma GmbH: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Göthert: Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel reimbursement; Incyte: Consultancy, Honoraria, Other: Travel reimbursement; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel reimbursement; Proteros Biostructures: Consultancy; AOP Orphan Pharmaceuticals: Honoraria, Other: Travel reimbursement; zr pharma&: Honoraria. Schafhausen: Swedish Orphan Biovitrum AB: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees. Brümmendorf: Novartis: Honoraria, Patents & Royalties, Research Funding; Janssen: Honoraria; Bristol Myers: Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Repeat Diagnostics: Research Funding; Takepart Media: Honoraria.

Background: Pelabresib (CPI-0610) is a potent, first-in-class, selective, oral small-molecule inhibitor of bromodomain and extraterminal domain (BET) proteins which is able to modify the expression of genes involved in nuclear factor kappa B (NFκB) signaling in patients with myelofibrosis (MF). Here we present results from MANIFEST (NCT02158858), an ongoing, global, open-label Phase 2 study investigating pelabresib monotherapy in patients with advanced MF who are intolerant/refractory to, or ineligible for ruxolitinib (RUX) and typically have very poor prognosis. Methods: Eligibility criteria are MF patients intolerant/refractory to or ineligible for JAKi, Dynamic International Prognostic Scoring System (DIPSS) risk category of ≥intermediate-2, platelets ≥75 × 10 9/L, and ≥2 symptoms measurable (score ≥1) per Myelofibrosis Symptom Assessment Form (MFSAF) v4.0. Additional criteria include red blood cell (RBC) transfusion dependent (TD) per Gale criteria in TD cohort or spleen volume of ≥450 cc by computed tomography/magnetic resonance imaging in non-TD cohort. Patients were enrolled as TD (defined as ≥2 U RBCs/month over 12 wks) and non-TD if TD criteria are not met. The primary endpoint in TD cohort is RBC transfusion independence (TI; defined as no transfusion for ≥12 wks), and ≥35% spleen volume reduction (SVR35) at wk 24 in the non-TD cohort. Secondary endpoints include number of patients with ≥50% total symptom score reduction (TSS50) per MFSAF v4.0 at wk 24, and safety. Additional exploratory endpoints include changes in plasma levels of proinflammatory cytokines and bone marrow (BM) morphology/fibrosis. Patients with assessment at wk ≥24 and those discontinuing after wk 12 are included in the analysis of the corresponding endpoint; these were the evaluable patients. Results: As of 29 September 2020, 27 pts were treated in the non-TD cohort for a median duration of 51 wks (2, 147 wks). At wk 24, 30% (7/23) evaluable pts achieved SVR35 (median change: -29%), and 48% (10/21) pts achieved TSS50 (median change: -56%). In the TD cohort, 19 pts were treated for a median duration of 32 wks (5, 78 wks). 21% (3/14) evaluable TD pts achieved RBC TI for ≥12 wks. Updated 24-wk data with a larger data set and new long-term data at 48 wks will be presented. Pt subgroup analyses revealed evidence of activity of pelabresib in a subset of pts who were ineligible to receive RUX, a patient population that generally has few therapeutic options. Clinical benefits observed with pelabresib included achievement of SVR35 and TSS50, improvements in bone marrow fibrosis, and increases in hemoglobin levels. A panel of 68 cytokines, including those known to be nuclear factor kappa B (NF-κB) targets linked to inflammation and elevated in MF pts, were evaluated in plasma samples obtained at baseline (BL) and during therapy. Cytokines were clustered to show different patterns of change during treatment with pelabresib. Overall, pelabresib significantly reduced plasma levels of several cytokines in RUX naïve or experienced pts (Figure). Cytokine changes with pelabresib in cluster 3 (which includes IL-6, CRP, RANTES, TNFa and IL-18, and is characterized by higher BL values and bigger decreases over time) and in cluster 5 (which includes EPO, TARC, ICAM-1 and IL-8, and is characterized by relatively lower BL values and less profound decreases over time) were more pronounced in RUX-naïve pts. 46 pts were evaluable for safety. The most common hematological treatment emergent adverse events (TEAEs) of any grade were thrombocytopenia (30%; ≥Grade 3: 15%) and anemia (15%; ≥Grade 3: 13%). The most common (≥20%) nonhematological TEAEs were nausea (39%; no ≥Grade 3), diarrhea (37%; ≥Grade 3: 4%), dysgeusia and asthenic conditions (30% each; no ≥Grade 3 for either), respiratory tract infections (28%; ≥Grade 3: 2%), cough (26%; no ≥Grade 3) and constipation and weight decrease (22% each; ≥Grade 3: 2% each). Conclusions: Preliminary data suggested pelabresib monotherapy was generally well tolerated and demonstrated signals of clinical activity in MF pts intolerant/refractory to or ineligible for JAKi, who have limited treatment options and poor outcomes. Figure 1 Figure 1. Disclosures Kremyanskaya: Astellas: Research Funding; Constellation: Research Funding; Incyte: Research Funding; Protagonist Therapeutics: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding; Astex: Research Funding; Chimerix: Research Funding. Mascarenhas: Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Galecto: Consultancy; Kartos: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Geron: Consultancy; Promedior: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forbius: Research Funding; CTI Biopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Constellation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merus: Research Funding; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy, Research Funding; Prelude: Consultancy. Palandri: Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Membership on an entity's Board of Directors or advisory committees; AOP: Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy. Vannucchi: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Verstovsek: Celgene: Consultancy, Research Funding; NS Pharma: Research Funding; AstraZeneca: Research Funding; CTI BioPharma: Research Funding; Promedior: Research Funding; Protagonist Therapeutics: Research Funding; Roche: Research Funding; Ital Pharma: Research Funding; PharmaEssentia: Research Funding; Blueprint Medicines Corp: Research Funding; Sierra Oncology: Consultancy, Research Funding; Gilead: Research Funding; Genentech: Research Funding; Incyte Corporation: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Constellation: Consultancy; Pragmatist: Consultancy. Harrison: Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Promedior: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AOP Orphan Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sierra Oncology: Honoraria; Incyte Corporation: Speakers Bureau; Constellation Pharmaceuticals: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Geron: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Keros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Galacteo: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Bose: CTI BioPharma: Honoraria, Research Funding; Blueprint Medicines: Honoraria, Research Funding; NS Pharma: Research Funding; Astellas: Research Funding; Promedior: Research Funding; Pfizer: Research Funding; Constellation Pharmaceuticals: Research Funding; Sierra Oncology: Honoraria; Kartos Therapeutics: Honoraria, Research Funding; Novartis: Honoraria; Celgene Corporation: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; BMS: Honoraria, Research Funding. Schiller: Ono-UK: Consultancy, Research Funding; Daiichi-Sankyo: Research Funding; Deciphera: Research Funding; FujiFilm: Research Funding; Stemline Therapeutics, Inc.: Honoraria, Research Funding, Speakers Bureau; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sangamo: Research Funding; Actuate: Research Funding; BMS/Celgene: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Constellation Pharmaceuticals: Research Funding; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Research Funding, Speakers Bureau; Geron: Research Funding; Genentech-Roche: Research Funding; Tolero: Research Funding; Takeda: Research Funding; Forma: Research Funding; Astellas: Honoraria, Research Funding, Speakers Bureau; Jazz: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gamida Cell Ltd.: Research Funding; Arog: Research Funding; Karyopharm: Research Funding; Onconova: Research Funding; Celator: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; PrECOG: Research Funding; Regimmune: Research Funding; Mateon: Research Funding; Kite/Gilead: Honoraria, Research Funding, Speakers Bureau; Samus: Research Funding; Bio: Research Funding; Delta-Fly: Research Funding; Trovagene: Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; Elevate: Research Funding; Novartis: Consultancy, Research Funding; Abbvie: Research Funding; Actinium Pharmaceuticals, Inc: Research Funding; Sanofi: Honoraria, Research Funding, Speakers Bureau; Pharma: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Biomed Valley Discoveries: Research Funding; Eli Lilly: Research Funding; ASH foundation: Other: Chair-unpaid; Sellas: Research Funding; Ono: Consultancy; Incyte: Consultancy; Ariad: Research Funding; AstraZeneca: Consultancy; Kaiser Permanente: Consultancy; Cyclacel: Research Funding; MedImmune: Research Funding; Ambit: Research Funding; Leukemia & Lymphoma Society: Research Funding; Bluebird Bio: Research Funding; Boehringer-Ingleheim: Research Funding; Cellerant: Research Funding; CTI Biopharma: Research Funding; Janssen: Research Funding; Kura Oncology: Research Funding; Pharmacyclics: Honoraria, Speakers Bureau; Millennium: Research Funding; National Marrow Donor Program: Research Funding; NIH: Research Funding; Onyx: Research Funding; Pharmamar: Research Funding; UC Davis: Research Funding; UCSD: Research Funding; Evidera: Consultancy; NCI: Consultancy; Novartis: Speakers Bureau. Rampal: Jazz Pharmaceuticals: Consultancy; BMS/Celgene: Consultancy; Stemline: Consultancy, Research Funding; Sierra Oncology: Consultancy; Novartis: Consultancy; Pharmaessentia: Consultancy; CTI: Consultancy; Abbvie: Consultancy; Blueprint: Consultancy; Disc Medicine: Consultancy; Memorial Sloan Kettering: Current Employment; Incyte: Consultancy, Research Funding; Kartos: Consultancy; Constellation: Research Funding. Drummond: BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Gupta: Sierra Oncology: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria; Pfizer: Consultancy; Constellation Pharma: Consultancy, Honoraria; Roche: Consultancy; Incyte: Honoraria, Research Funding; BMS-Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Patriarca: Novartis: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Incyte: Honoraria; Pfizer: Honoraria; Argenix: Honoraria. Scandura: Constellation: Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MPN-RF (Foundation): Research Funding; CR&T (Foudation): Research Funding; European Leukemia net: Honoraria, Other: travel fees . Teichmann: Pfizer: Membership on an entity's Board of Directors or advisory committees. Hoffman: Novartis: Other: Data Safety Monitoring Board, Research Funding; Protagonist Therapeutics, Inc.: Consultancy; AbbVie Inc.: Other: Data Safety Monitoring Board, Research Funding; Kartos Therapeutics, Inc.: Research Funding. Colak: Constellation Pharmaceuticals: Current Employment. Ren: Constellation Pharmaceuticals: Current Employment. Bobba: Constellation Pharmaceuticals: Current Employment. Cui: Constellation Pharmaceuticals: Current Employment. Efuni: Constellation Pharmaceuticals: Current Employment. Talpaz: Imago: Consultancy; Constellation: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Grant/research support ; Celgene: Consultancy; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

The inducible T cell costimulator (ICOS) is a potent promoter of organ inflammation in murine lupus. ICOS stimulates T follicular helper cell differentiation in lymphoid tissue, suggesting that it might drive autoimmunity by enhancing autoantibody production. Yet the pathogenic relevance of this mechanism remains unclear. It is also unknown whether other ICOS-induced processes might contribute to lupus pathology. Here we show that selective ablation of ICOS ligand (ICOSL) in CD11c(+) cells, but not in B cells, dramatically ameliorates kidney and lung inflammation in lupus-prone MRL.Fas(lpr) mice. Autoantibody formation was largely unaffected by ICOSL deficiency in CD11c(+) cells. However, ICOSL display by CD11c(+) cells in inflamed organs had a nonredundant role in protecting invading T cells from apoptosis by elevating activity of the PI3K-Akt signaling pathway, thereby facilitating T cell accrual. These findings reveal a mechanism that locally sustains organ inflammation in lupus.

Mice repopulated with human hematopoietic cells are a powerful tool for the study of human hematopoiesis and immune function in vivo. However, existing humanized mouse models cannot support development of human innate immune cells, including myeloid cells and natural killer (NK) cells. Here we describe two mouse strains called MITRG and MISTRG, in which human versions of four genes encoding cytokines important for innate immune cell development are knocked into their respective mouse loci. The human cytokines support the development and function of monocytes, macrophages and NK cells derived from human fetal liver or adult CD34(+) progenitor cells injected into the mice. Human macrophages infiltrated a human tumor xenograft in MITRG and MISTRG mice in a manner resembling that observed in tumors obtained from human patients. This humanized mouse model may be used to model the human immune system in scenarios of health and pathology, and may enable evaluation of therapeutic candidates in an in vivo setting relevant to human physiology.

SummaryDetection of self nucleic acids by Toll-like receptors (TLR) preciptates autoimmune diseases, including systemic lupus erythematosus (SLE). It remains unknown how TLR signals in specific cell types contribute to distinct manifestations of SLE. Here, we demonstrate that formation of anti-nuclear antibodies in MRL.Faslpr mice entirely depends on the TLR signaling adaptor MyD88 in B cells. Further, MyD88 deficiency in B cells ameliorated nephritis, including antibody-independent interstitial T cell infiltrates, suggesting that nucleic acid-specific B cells activate nephrotoxic T cells. Surprisingly, MyD88 deletion in dendritic cells (DCs) did not affect nephritis, despite the importance of DCs in renal inflammation. In contrast, MyD88 in DCs was critical for dermatitis, revealing a separate pathogenetic mechanism. DC-expressed MyD88 promoted interferon-α production by plasmacytoid DCs, which was associated with Death domain-associated protein 6 upregulation and B lymphopenia. Our findings thus reveal unique immunopathological consequences of MyD88 signaling in B cells and DCs in lupus.

Summary Dendritic cells (DCs) initiate and control the adaptive immune response against infections. However, their contributions to the anti-self adaptive immune response in autoimmune disorders like systemic lupus erythematosus are uncertain. By constitutively deleting DCs in MRL. Fas lpr mice, we show that they have complex roles in murine lupus. The net effect of DC deletion was to ameliorate disease. DCs were crucial for the expansion and differentiation of T cells but, surprisingly, not required for their initial activation. Correspondingly, kidney interstitial infiltrates developed in the absence of DCs, but failed to progress. DC deletion concomitantly decreased inflammatory and regulatory T cell numbers. Unexpectedly, plasmablast numbers and autoantibody concentrations depended on DCs, in contrast to total serum immunoglobulin concentrations, suggesting an effect of DCs on extrafollicular humoral responses. These findings reveal that DCs operate in unanticipated ways in murine lupus and validate them as a potential therapeutic target in autoimmunity.

Nat. Biotechnol. 32, 364–372 (2014); published online 16 March 2014; corrected after print 8 November 2017 In the version of this article initially published, the cells labeled Me290 were Me275 cells. Both Me275 and Me290 are human metastatic HLA-A201+ melanoma cell lines, and both of them were obtained from the Ludwig Cancer Institute.

B cells contribute to the pathogenesis of chronic autoimmune disorders, like systemic lupus erythematosus (SLE), via multiple effector functions. However, B cells are also implicated in regulating SLE and other autoimmune syndromes via release of IL-10. B cells secreting IL-10 were termed “Bregs” and were proposed as a separate subset of cells, a concept that remains controversial. The balance between pro- and anti-inflammatory effects could determine the success of B cell-targeted therapies for autoimmune disorders; therefore, it is pivotal to understand the significance of B cell-secreted IL-10 in spontaneous autoimmunity. By lineage-specific deletion of Il10 from B cells, we demonstrated that B cell-derived IL-10 is ineffective in suppressing the spontaneous activation of self-reactive B and T cells during lupus. Correspondingly, severity of organ disease and survival rates in mice harboring Il10-deficient B cells are unaltered. Genetic marking of cells that transcribe Il10 illustrated that the pool of IL-10–competent cells is dominated by CD4 T cells and macrophages. IL-10–competent cells of the B lineage are rare in vivo and, among them, short-lived plasmablasts have the highest frequency, suggesting an activation-driven, rather than lineage-driven, phenotype. Putative Breg phenotypic subsets, such as CD1dhiCD5+ and CD21hiCD23hi B cells, are not enriched in Il10 transcription. These genetic studies demonstrated that, in a spontaneous model of murine lupus, IL-10–dependent B cell regulation does not restrain disease and, thus, the pathogenic effects of B cells are not detectably counterbalanced by their IL-10–dependent regulatory functions.

B cells play important roles in autoimmune diseases ranging from multiple sclerosis to rheumatoid arthritis. B cells have also long been considered central players in systemic lupus erythematosus. However, anti-CD20–mediated B cell depletion was not effective in two clinical lupus studies, whereas anti-B lymphocyte stimulator, which inhibits B cell survival, was effective. Others and we previously found that anti-CD20–based depletion was surprisingly ineffective in tissues of lupus-prone mice, but that persistent high doses eventually led to depletion and ameliorated lupus. Lupus patients might also have incomplete depletion, as suggested in several studies, and which could have led to therapeutic failure. In this study, we investigated the mechanism of resistance to Ab-mediated cellular depletion in murine lupus. B cells from lupus-prone mice were easily depleted when transferred into normal environments or in lupus-prone mice that lacked serum Ig. Serum from lupus-prone mice transferred depletion resistance, with the active component being IgG. Because depletion is FcγR-dependent, we assayed macrophages and neutrophils exposed to lupus mouse serum, showing that they are impaired in IgG-mediated phagocytosis. We conclude that depletion resistance is an acquired, reversible phagocytic defect depending on exposure to lupus serum IgG. These results have implications for optimizing and monitoring cellular depletion therapy.

Platelets play a crucial role in the physiology of primary hemostasis and pathophysiological processes such as arterial thrombosis. Accumulating evidence suggests a key regulatory role of both NO and reactive oxygen species (ROS) in platelets. While the inhibitory role of NO/cGMP signaling in both murine and human platelets is well established, recent data suggest that intracellular ROS generation is involved in platelet activation. Thrombin-induced intracellular ROS production was inhibited by NAD(P)H oxidase inhibitors (DPI and apocynin), cyclooxygenase inhibitor (acetylsalicylic acid), and superoxide scavengers (tiron and MnTMPyP). Furthermore, thrombin (Trap6)-induced platelet aggregation and thrombus formation on collagen under high shear was inhibited by NAD(P)H oxidase inhibitors (DPI and apocynin), whereas secretion and platelet shape change were not affected. Inhibition of alphaIIbbeta3 activation by NAD(P)H oxidase inhibitors and superoxide scavengers was independent of NO/cGMP signaling demonstrating a direct role of platelet NAD(P)H oxidase-generated ROS for integrin alphaIIbbeta3 activation.