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Granulocyte colony-stimulating factor (G-CSF) is widely used to enhance myeloid recovery after chemotherapy and to mobilize hematopoietic stem cells (HSCs) for transplantation. Unfortunately, through the course of chemotherapy, cancer patients can acquire leukemogenic mutations that cause therapy-related myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). This raises the question of whether therapeutic G-CSF might potentiate therapy-related MDS/AML by disproportionately stimulating mutant HSCs and other myeloid progenitors. A common mutation in therapy-related MDS/AML involves chromosome 7 deletions that inactivate many tumor suppressor genes, including KMT2C. Here, we show that Kmt2c deletions hypersensitize murine HSCs and myeloid progenitors to G-CSF, as evidenced by increased HSC mobilization and enhanced granulocyte production from granulocyte-monocyte progenitors (GMPs). Furthermore, Kmt2c attenuates the G-CSF response independently from its SET methyltransferase function. Altogether, the data raise concerns that monosomy 7 can hypersensitize progenitors to G-CSF, such that clinical use of G-CSF may amplify the risk of therapy-related MDS/AML., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Type I interferon (IFN-1) regulates gene expression and hematopoiesis both during development and in response to inflammatory stress. We previously showed that during development in mice, hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) induce IFN-1 target genes shortly before birth. This coincides with the onset of a transition to adult hematopoiesis, and it drives the expression of genes associated with antigen presentation. However, it is not clear whether perinatal IFN-1 modulates hematopoietic output, as has been observed in contexts of inflammation. We have characterized hematopoiesis at several different stages of blood formation, from HSCs to mature blood cells, and found that loss of the IFN-1 receptor (IFNAR1) leads to depletion of several phenotypic HSC and MPP subpopulations in neonatal and juvenile mice. Committed lymphoid and myeloid progenitor populations expand simultaneously. These changes had a surprisingly little effect on the production of more differentiated blood cells. Cellular indexing of transcriptomes and epitopes by sequencing resolved the discrepancy between the extensive changes in progenitor numbers and modest changes in hematopoiesis, revealing stability in most MPP populations in Ifnar1-deficient neonates when the populations were identified based on gene expression rather than surface marker phenotype. Thus, basal IFN-1 signaling has only modest effects on hematopoiesis. Discordance between transcriptionally and phenotypically defined MPP populations may affect interpretations of how IFN-1 shapes hematopoiesis in other contexts, such as aging or inflammation., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Acute myeloid leukemia (AML) initiation requires multiple rate-limiting mutations to cooperatively reprogram progenitor cell identity. For example, FLT3 internal tandem duplication (FLT3ITD) mutations cooperate with a variety of different initiating mutations to reprogram myeloid progenitor fate. These initiating mutations often skew toward either pediatric or adult AML patient populations, though FLT3ITD itself occurs at similar frequencies in both age groups. This raises the question of whether FLT3ITD might induce distinct transcriptional programs and unmask distinct therapeutic vulnerabilities when paired with pediatric, as opposed to adult AML-initiating mutations. To explore this possibility, we compared AML evolution in mice that carried Flt3ITD/NUP98-HOXD13 (NHD13) or Flt3ITD/Runx1DEL mutation pairs, which are respectively most common in pediatric and adult AML. Single-cell analyses and epigenome profiling revealed distinct interactions between Flt3ITD and its cooperating mutations. Whereas Flt3ITD and Flt3ITD/Runx1DEL caused aberrant expansion of myeloid progenitors, Flt3ITD/NHD13 drove the emergence of a pre-AML population that did not resemble normal hematopoietic progenitors. Differences between Flt3ITD/Runx1DEL and Flt3ITD/NHD13 cooperative target gene expression extended to fully transformed AML as well. Flt3ITD/NHD13 cooperative target genes were enriched in human NUP98-translocated AML. Flt3ITD/NHD13 selectively hijacked type I interferon signaling to drive expansion of the pre-AML population. Blocking interferon signaling delayed AML initiation and extended survival. Thus, common AML driver mutations, such as FLT3ITD, can coopt different mechanisms of transformation in different genetic contexts. Furthermore, pediatric-biased NUP98 fusions convey actionable interferon dependence., (© 2023 by The American Society of Hematology.)

The myeloid tumor suppressor KMT2C is recurrently deleted in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), particularly therapy-related MDS/AML (t-MDS/t-AML), as part of larger chromosome 7 deletions. Here, we show that KMT2C deletions convey a selective advantage to hematopoietic stem cells (HSCs) after chemotherapy treatment that may precipitate t-MDS/t-AML. Kmt2c deletions markedly enhance murine HSC self-renewal capacity without altering proliferation rates. Haploid Kmt2c deletions convey a selective advantage only when HSCs are driven into cycle by a strong proliferative stimulus, such as chemotherapy. Cycling Kmt2c-deficient HSCs fail to differentiate appropriately, particularly in response to interleukin-1. Kmt2c deletions mitigate histone methylation/acetylation changes that accrue as HSCs cycle after chemotherapy, and they impair enhancer recruitment during HSC differentiation. These findings help explain why Kmt2c deletions are more common in t-MDS/t-AML than in de novo AML or clonal hematopoiesis: they selectively protect cycling HSCs from differentiation without inducing HSC proliferation themselves., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Fetal and adult hematopoietic stem cells (HSCs) have distinct proliferation rates, lineage biases, gene expression profiles, and gene dependencies. Although these differences are widely recognized, it is not clear how the transition from fetal to adult identity is coordinated. Here we show that murine HSCs and committed hematopoietic progenitor cells (HPCs) undergo a gradual, rather than precipitous, transition from fetal to adult transcriptional states. The transition begins prior to birth and is punctuated by a late prenatal spike in type I interferon signaling that promotes perinatal HPC expansion and sensitizes progenitors to the leukemogenic FLT3 ITD mutation. Most other changes in gene expression and enhancer activation are imprecisely timed and poorly coordinated. Thus, heterochronic enhancer elements, and their associated transcripts, are activated independently of one another rather than as part of a robust network. This simplifies the regulatory programs that guide neonatal HSC/HPC ontogeny, but it creates heterogeneity within these populations., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

MLL rearrangements are translocation mutations that cause both acute lymphoblastic leukemia and acute myeloid leukemia (AML). These translocations can occur as sole clonal driver mutations in infant leukemias, suggesting that fetal or neonatal hematopoietic progenitors may be exquisitely sensitive to transformation by MLL fusion proteins. To test this possibility, we used transgenic mice to induce one translocation product, MLL-ENL , during fetal, neonatal, juvenile and adult stages of life. When MLL-ENL was induced in fetal or neonatal mice, almost all died of AML. In contrast, when MLL-ENL was induced in adult mice, most survived for >1 year despite sustained transgene expression. AML initiation was most efficient when MLL-ENL was induced in neonates, and even transient suppression of MLL-ENL in neonates could prevent AML in most mice. MLL-ENL target genes were induced more efficiently in neonatal progenitors than in adult progenitors, consistent with the distinct AML initiation efficiencies. Interestingly, transplantation stress mitigated the developmental barrier to leukemogenesis. Since fetal/neonatal progenitors were highly competent to initiate MLL-ENL -driven AML, we tested whether Lin28b , a fetal master regulator, could accelerate leukemogenesis. Surprisingly, Lin28b suppressed AML initiation rather than accelerating it. This may explain why MLL rearrangements often occur before birth in human infant leukemia patients, but transformation usually does not occur until after birth, when Lin28b levels decline. Our findings show that the efficiency of MLL-ENL -driven AML initiation changes through the course of pre- and postnatal development, and developmental programs can be manipulated to impede transformation., (© 2019 by The American Society of Hematology.)

Signaling through the leukocyte function-associated antigen 1 (LFA-1) molecule has previously been shown to induce homotypic aggregation in T cells and to induce cytoskeletal changes in T lymphoma cells. In this study we describe the induction of a dendritic phenotype associated with cytoskeletal rearrangement in activated human peripheral blood T cells stimulated with monoclonal antibody SPV-L7 to LFA-1 alpha. Maximal expression of this phenotype required 72 h preactivation with phorbol myristate acetate and expression was abolished using the protein kinase C inhibitor staurosporine. Monoclonal antibody to CD18, the beta-chain of LFA-1, did not induce this phenotype. Monoclonal antibody MEM 83 to presumably a discrete epitope on LFA-1 alpha did not induce this phenotype but induced homotypic aggregation. However, a monoclonal antibody to CD44 induced a similar phenotype in activated lymphocytes. Induction of both homotypic in activated lymphocytes. Induction of both homotypic aggregation and the dendritic phenotype was abolished by preincubation with soluble intracellular adhesion molecule 1 (ICAM-1). Cytoskeletal inhibitors prevented the morphological changes in SPV-L7-activated lymphocytes. Preincubation with tyrosine kinase inhibitor, protein kinase C inhibitors, and inhibitors of new protein synthesis also prevented these morphological changes. These data suggest that discrete epitopes on LFA-1 alpha may be capable of inducing discrete signals either for homotypic aggregation or for a dendritic phenotype. As both LFA-1 and CD44 are involved in the migration of lymphocytes through high endothelial venules, these data could suggest that these molecules transduce signals resulting in cytoskeletal modification necessary for lymphocyte transmigration.

To determine the role of Gly-1 and Lys-2 of bovine gamma B-crystallin in glycation and cross-linking, Lys-2 was changed to Thr by site-directed mutagenesis. A polymerase chain reaction was used to perform site-directed mutagenesis on the third codon (AAG-->ACG) of bovine gamma B-crystallin cDNA. The wild type and mutant cDNAs were cloned into pMON5743 and expressed in JM101 Escherichia coli cells, and the identity of gamma B-crystallin was confirmed by Western blotting after purification by cation exchange high performance liquid chromatography. Glycation of gamma B-crystallin by [14C]glucose was reduced significantly due to the mutation of Lys-2, supporting the view that Lys-2 is a major glycation site. Peptide mapping showed the presence of two major labeled peptides containing N-terminal sequences, and in the mutant these peptides had longer retention times and reduced radioactivity. Amino acid analysis, after glycation with [14C]glucose, revealed N-terminal glycine as the most predominant glycation site. Lys-2 was glycated slower than Gly-1 but faster than Lys-163. Glycation with DL-glyceraldehyde showed an important role for both Gly-1 and Lys-2 in the glycation-mediated gamma B-crystallin cross-linking.

Objectives: To investigate the involvement of the adhesion molecule CD44 in the homing of lymphocytes to synovial tissue, by examining the density of expression and molecular mass of CD44 on rheumatoid synovial fluid lymphocytes., Methods: Twenty patients with rheumatoid arthritis were studied. Peripheral blood and synovial fluid lymphocytes were isolated by Ficoll-Hypaque sedimentation. CD44 expression was analysed by two colour flow cytometry of CD3 positive T lymphocytes with calculation of mean fluorescence intensity. Expression of activation markers M21C5, M2B3, interleukin (IL)-2 receptor and transferrin receptor was quantitated. In addition, CD44 molecular mass was examined by Western blot in six patients., Results: CD44 expression was markedly increased on synovial fluid T lymphocytes of rheumatoid patients relative to peripheral blood lymphocytes from the same individuals. CD44 molecular mass on peripheral blood mononuclear cells was 88 kDa, but that on synovial fluid lymphocytes was only 83 kDa. CD44 expression correlated significantly with expression of activation markers M21C5, M2B3, and the IL-2 receptor., Conclusions: Alterations in density of expression or of the molecular mass of CD44 could contribute to local tissue injury, either directly by facilitating adhesion, or indirectly through effects on other adhesion molecules.

We describe four patients with rheumatoid arthritis and unilateral upper limb oedema. In all cases, qualitative lymphoscintigraphy showed lymphatic obstruction in the affected limb.

A 52 year old man developed progressive painful swelling of both calves and difficulty walking. Physical examination showed asymmetrical localised swelling with induration and tenderness on palpation. Peripheral blood eosinophilia was noted. Biopsy of deep fascia and muscle showed typical features of eosinophilic fasciitis. He was treated with non-steroidal anti-inflammatory drugs and intensive physiotherapy. The clinical features had completely resolved six months later.

The expression of intermediate filaments in normal cells is mainly determined by their embryonal developmental origin. Flow cytometry using monoclonal antibody RT97 demonstrated that neurofilament was detectable in the human HuT 78 T-cell line and on resting T lymphocytes. Expression was greatly increased on lymphocytes activated for 3 days with phorbol ester. Western blotting confirmed the presence of the 200,000 MW form of neurofilament in T lymphocytes. Stimulation of peripheral blood T cells with phorbol myristate acetate (PMA) or with anti-CD3 monoclonal antibodies resulted in a marked increase in detection of phosphorylated neurofilament on Western blotting. Stimulation of HuT 78 cells with anti-LFA-1 resulted in redistribution of neurofilament from a perinuclear spheroid core into dendritic processes. These data indicate that T cells activated through the T-cell receptor associated complex express an intermediate filament usually associated with neurally derived cells. The finding that neurofilament expression and organization are regulated by T-cell surface molecules suggests a role for this intermediate filament in T-cell function.

In this prospective study of 24 pregnant patients with rheumatoid arthritis, quiescent disease activity in 21 patients (88%) during gestation was followed by more active disease in the puerperium in 19 patients (79%). Increased disease activity was reflected in a deterioration in manual dexterity and this was found to correlate with a post-partum rise in IgM rheumatoid factor (IgM RF) (r = 0.86) and a post-partum decline in pregnancy associated alpha-2 glycoprotein (PAG) (r = 0.44). The increase in IgM RF also correlated with increased disease activity measured by a visual analogue scale (r = 0.44). Changes in IgA RF were not observed. These results suggest that PAG and IgM RF could contribute to the modulation and pathogenesis of rheumatoid arthritis during pregnancy.

The use of injectable gold in the treatment of rheumatoid arthritis (RA) is hampered by the high incidence of adverse reactions of which myelotoxicity is potentially the most serious. Regular full blood count (FBC) monitoring prior to each injection, a practice which requires much time and effort, has never been fully evaluated. Of 154 patients who were started on gold and followed by the lifetable method for up to 10 years, five patients were withdrawn from treatment because of myelotoxicity, thrombocytopenia in all cases: the two most serious cases occurred early at 3 and 7 months after starting treatment; three mild cases occurred at 17, 37 and 60 months, were of slow onset and reversed spontaneously. Clearly, FBC monitoring is justifiable in the first two years of treatment when the incidence of adverse reaction is highest. Further investigation is required to justify this practice after two years of uncomplicated treatment.

Values for alkaline phosphatase and gamma glutamyl transpeptidase (GGTP) and the prevalence of their elevation was significantly higher in 35 patients with ankylosing spondylitis (AS) than in 35 age and sex matched controls. The abnormal enzyme levels appeared to reflect a non-specific reaction to inflammation and could thus aid in assessment of disease status.

Nerve conduction studies have been carried out pre- and postoperatively on 26 hands of patients with a carpal tunnel syndrome. When examined six to eight weeks postoperatively, there had been no significant change in conduction velocity or action potential amplitude in the fingers distal to the compression. Velocity had increased over the carpal tunnel segment. When the patients were seen between 12 and 18 weeks postoperatively, velocity and amplitude had increased in the fingers. The group with marked electrical abnormalities had improved more than the group in which digital amplitude was originally within the control range. The improvement occurred too early to be due to regeneration after relief of compression. It is suggested that either maturation of regenerating fibres was delayed by the compression or a reversible change had occurred in surviving fibres.

Nerve conduction studies were carried out on 16 alcoholic subjects with minimal or no clinical evidence of peripheral neuropathy. Digital nerve action potentials recorded at the base of the finger were reduced in amplitude in five but the potential at the wrist was reduced in only one. In two other patients, even though the values were within the control range, the ratio of the amplitude recorded from the finger and from the wrist was smaller than in control subjects. Thus, by recording both digital and wrist action potentials, abnormalities have been demonstrated in seven of 16 patients, whereas the wrist potential was abnormal in only one. Conduction velocity was slightly reduced in the fingers in three patients.

A technique is described for stimulating and recording from nerves in the finger using surface electrodes. A decrease in amplitude and velocity was found with increasing age. In control subjects the digital potential was approximately one and a half times larger than the potential recorded at the wrist. In patients with carpal tunnel syndrome there was some reduction in amplitude and velocity of the digital potential, but the changes were more marked at the wrist. In diabetic patients more uniform changes were found in the two segments. The technique was particularly useful in enabling conduction velocity to be calculated in the digital nerves when no potential could be recorded at the wrist.

A clinical follow-up study of 12 patients with diabetic amyotrophy is reported. Re-examination after an interval indicated that improvement had occurred in all but one instance, and had been maintained over an average follow-up period of four and a half years. Improvement in the neurological syndrome appeared to follow improvement in diabetic control or institution of treatment in those whose diabetes had not previously been diagnosed.Seven patients made a good functional recovery, three no longer having any muscular weakness. Five showed significant residual disability.