CD207+CD1a+ cells circulate in pediatric patients with active Langerhans cell histiocytosis

Circulating monocytes decrease significantly following disease-directed therapy and may reflect disease expansion in Langerhans Cell Histiocytosis

We aimed to examine the association between relative monocytosis and the recurrence of pulmonary Langerhans Cell Histiocytosis. Clinical, laboratory, radiographic and treatment data for 86 patients with a histopathological diagnosis of Langerhans Cell Histiocytosis over a 20-year duration. Parameters such as biological sex, age at diagnosis, time to diagnosis, molecular diagnostic data and imaging were collected. Treatment responses were assessed predominantly through radiography, with RECIST 1.1 criteria applied to MRI or CT scans and PERCIST utilized for serial PET imaging. Investigators also assessed peripheral blood absolute monocyte count at various time points, including initial diagnosis and the most recently available value. While peripheral blood absolute monocyte count between the earliest assessed timepoint and latest value did not differ, the mean value on progression (0.94 K/µL), however, was significantly higher than that following re-institution of therapy (0.31, p = 0.000794. Our observation of relative monocytosis on LCH disease progression may be related to an increase in circulating LCH on disease progression or from increased monocyte production for later differentiation into mature dendritic cells that participate in MHC Class 1 upregulation. This trend is especially evident in pulmonary LCH which is incited by tissue trauma and irritation by environmental factors. The phenomena observed in our study parallel other non-LCH cohorts, specifically in published findings from our own group in patients with Rosai Dorfman and Erdheim Chester Disease. To further elucidate the molecular underpinnings of LCH and explore the etiology of this monocyte trend, expanded integrated genomic-transcriptomic sequencing analyses to evaluate the molecular character of LCH and ultimately clarify the origin of this monocyte trend are in progress. These studies are poised to offer invaluable insight to the molecular mechanisms underlying LCH, specifically as they pertain to monocyte signaling and differentiation.

Increased AXLhigh myeloid cells as pathognomonic marker in Langerhans cell histiocytosis and Langerin expression dependence of mTOR inhibition

Langerhans cell histiocytosis (LCH) is characterized by an expansion and accumulation of pathological histiocytes expressing langerin (CD207) and CD1a in different organs under an inflammatory milieu. The origin of pathognomonic precursors of LCH is widely debated, but monocytes and pre-dendritic cells (pre-DC) play a significant role. Remarkably, we found an expansion of AXLhigh cells in the CD11c+ subset of patients with active LCH, which also express the pathognomonic CD207 and CD1a. Moreover, we obtained a monocyte-derived LC-like (mo-LC-like) expressing high levels of AXL when treated with inflammatory cytokine, or plasma of patients with active disease. Intriguingly, inhibiting the mTOR pathway at the initial stages of monocyte differentiation to LC-like fosters the pathognomonic LCH program, highly increasing CD207 levels, together with NOTCH1 induction. We define here that AXLhigh could also be taken as a strong pathognomonic marker for LCH, and the release of Langerin and NOTCH1 expression depends on the inhibition of the mTOR pathway.

Chlamydia trachomatis enhances HPV persistence through immune modulation

Chlamydia trachomatis (CT) is the most common sexually transmitted infections globally, and CT infection can enhance HPV persistence. Epidemiological analysis has shown that patients with CT/HPV coinfection have a higher risk of developing cervical cancer and exhibit more rapid progression to cervical cancer than patients with HPV infection alone. However, the mechanism has not been fully elucidated. Here, we report that CT infection supports HPV persistence by further suppressing the functions of Langerhans cells (LCs); in particular, CT further activates the PI3K pathway and inhibits the MAPK pathways in LCs, and these pathways are frequently involved in the regulation of immune responses. CT/HPV coinfection also impairs LC functions by reducing the antigen-presenting ability and density of LCs. Moreover, CT/HPV coinfection can alter T-cell subsets, resulting in fewer CD4 + and CD8 + T cells and more infiltrating Tregs. Moreover, CT/HPV coinfection decreases the CD4 + /CD8 + T cell ratio to below 1, coinfection also induces greater T lymphocytes' apoptosis than HPV infection, thus impairing cell-mediated immunity and accelerating the progress to cervical cancer.

Monitoring Circulating CD207+CD1a+ Cells in Langerhans Cell Histiocytosis and Clinical Implications

Langerhans cell histiocytosis (LCH) is a disorder characterized by an abnormal accumulation of CD207⁺ and CD1a⁺ cells in almost any tissue. Currently, there is a lack of prognostic markers to follow up patients and track disease reactivation or treatment response. Putative myeloid precursors CD207⁺ and CD1a⁺ cells were previously identified circulating in the blood. Therefore, we aim to develop a sensitive tracing method to monitor circulating CD207⁺ and CD1a⁺ cells in a drop of blood sample of patients with LCH. A total of 202 blood samples from patients with LCH and 23 controls were tested using flow cytometry. A standardized cellular score was defined by quantifying CD207⁺ and CD1a⁺ expression in monocytes and dendritic cells, based on CD11b, CD14, CD11c, and CD1c subpopulations, resulting in a unique value for each sample. The scoring system was validated by a receiver operating characteristic curve showing a reliable discriminatory capacity (area under the curve of 0.849) with a threshold value of 14, defining the presence of circulating CD207⁺ and CD1a⁺ cells. Interestingly, a fraction of patients with no evident clinical manifestation at the time of sampling also showed presence of these cells (29.6%). We also found a differential expression of CD207 and CD1a depending on the organ involvement, and a positive correlation between the cellular score and plasma inflammatory markers such as soluble CD40L, soluble IL-2Ra, and CXCL12. In conclusion, the analysis of circulating CD207 and CD1a cells in a small blood sample will allow setting a cellular score with minimal invasiveness, helping with prognostic accuracy, detecting early reactivation, and follow-up.

Plasma Signaling Factors in Patients With Langerhans Cell Histiocytosis (LCH) Correlate With Relative Frequencies of LCH Cells and T Cells Within Lesions

Langerhans cell histiocytosis (LCH) lesions contain an inflammatory infiltrate of immune cells including myeloid-derived LCH cells. Cell-signaling proteins within the lesion environment suggest that LCH cells and T cells contribute majorly to the inflammation. Foxp3+ regulatory T cells (Tregs) are enriched in lesions and blood from patients with LCH and are likely involved in LCH pathogenesis. In contrast, mucosal associated invariant T (MAIT) cells are reduced in blood from these patients and the consequence of this is unknown. Serum/plasma levels of cytokines have been associated with LCH disease extent and may play a role in the recruitment of cells to lesions. We investigated whether plasma signaling factors differed between patients with active and non-active LCH. Cell-signaling factors (38 analytes total) were measured in patient plasma and cell populations from matched lesions and/or peripheral blood were enumerated. This study aimed at understanding whether plasma factors corresponded with LCH cells and/or LCH-associated T cell subsets in patients with LCH. We identified several associations between plasma factors and lesional/circulating immune cell populations, thus highlighting new factors as potentially important in LCH pathogenesis. This study highlights plasma cell-signaling factors that are associated with LCH cells, MAIT cells or Tregs in patients, thus they are potentially important in LCH pathogenesis. Further study into these associations is needed to determine whether these factors may become suitable prognostic indicators or therapeutic targets to benefit patients.

Does CD1a Expression Influence T Cell Function in Patients With Langerhans Cell Histiocytosis?

Langerhans cell histiocytosis lesions are characterized by CD1a+ myeloid lineage LCH cells and an inflammatory infiltrate of cytokines and immune cells, including T cells. T cells that recognize CD1a may be implicated in the pathology of many disease states including cancer and autoimmunity but have not been studied in the context of LCH despite the expression of CD1a by LCH cells. In this perspective article, we discuss the expression of CD1a by LCH cells, and we explore the potential for T cells that recognize CD1a to be involved in LCH pathogenesis.

High prevalence of BRAFV600E in patients with cholestasis, sclerosing cholangitis or liver fibrosis secondary to Langerhans cell histiocytosis

Targeted therapies with MAPK inhibitors have proven to modulate the clinical manifestations of patients with Langerhans cell histiocytosis (LCH). We explored the presence of BRAF^V600E mutation in our cohort of patients with LCH and cholestasis, sclerosing cholangitis, or liver fibrosis that presented resistance to chemotherapy. The BRAF^V600E mutation was detected either in the diagnosis (skin and bone) or liver biopsy in our cohort of 13 patients. Thus, we observed a high incidence of BRAF^V600E mutation in 100% either in diagnostic biopsy (skin and bone) or liver biopsy in patients with progressive liver disease, sequela, or liver transplant requirement.

Langerhans cell histiocytosis: Presentation in a preterm neonate

Background

Langerhans cell histiocytosis (LCH) is a rare disorder in which Langerhans cells (LC) accumulate in the skin or other organs and cause tumor formation or organ damage. Cutaneous lesions can vary widely and do not predict extent of systemic disease or prognosis.

Case

We present a premature infant with skin findings, multisystem involvement, and immunohistochemical markers consistent with multisystem LCH.

Conclusion

Limited data from preterm neonates with LCH suggest that prognosis is particularly poor, with even limited cutaneous disease often rapidly progressing to become fatal, although diagnosis is not always prompt. Early diagnosis and treatment may affect prognosis.

A Heterotypic Tridimensional Model to Study the Interaction of Macrophages and Glioblastoma In Vitro

Background: Glioblastoma multiforme (GBM) is the most frequent and aggressive primary brain tumor, and macrophages account for 30–40% of its composition. Most of these macrophages derive from bone marrow monocytes playing a crucial role in tumor progression. Unraveling the mechanisms of macrophages-GBM crosstalk in an appropriate model will contribute to the development of specific and more successful therapies. We investigated the interaction of U87MG human GBM cells with primary human CD14⁺ monocytes or the THP-1 cell line with the aim of establishing a physiologically relevant heterotypic culture model. Methods: primary monocytes and THP-1 cells were cultured in the presence of U87MG conditioned media or co-cultured together with previously formed GBM spheroids. Monocyte differentiation was determined by flow cytometry. Results: primary monocytes differentiate to M2 macrophages when incubated with U87MG conditioned media in 2-dimensional culture, as determined by the increased percentage of CD14⁺CD206⁺ and CD64⁺CD206⁺ populations in CD11b⁺ cells. Moreover, the mitochondrial protein p32/gC1qR is expressed in monocytes exposed to U87MG conditioned media. When primary CD14⁺ monocytes or THP-1 cells are added to previously formed GBM spheroids, both invade and establish within them. However, only primary monocytes differentiate and acquire a clear M2 phenotype characterized by the upregulation of CD206, CD163, and MERTK surface markers on the CD11b⁺CD14⁺ population and induce alterations in the sphericity of the cell cultures. Conclusion: our results present a new physiologically relevant model to study GBM/macrophage interactions in a human setting and suggest that both soluble GBM factors, as well as cell-contact dependent signals, are strong inducers of anti-inflammatory macrophages within the tumor niche.

BRAF V600E Mutation in Cell-Free DNA, Rather than in Lesion Tissues, at Diagnosis Is An Independent Prognostic Factor in Children with Langerhans Cell Histiocytosis

The aim of this study was to investigate the prognostic significance of BRAF^V600E in cell-free (cf) DNA (cfBRAF^V600E) and lesion tissues (ltBRAF^V600E) in pediatric Langerhans cell histiocytosis (LCH). This study included a total of 140 patients with successfully detected cfBRAF^V600E and ltBRAF^V600E at diagnosis. Treatment response at week 6 was correlated with both cfBRAF^V600E and ltBRAF^V600E Moreover, the patients with positive cfBRAF^V600E had a much lower 3-year progression-free survival (PFS) rate and a higher progression/reactivation rate than those with negative cfBRAF^V600E (47.1% ± 7.6% vs. 78.4% ± 5.1%, P < 0.0001; 44.6% vs. 19.0%, P = 0.001, respectively). However, no significant difference was found in the 3-year PFS rate or progression/reactivation rate between patients with positive and negative ltBRAF^V600E (P = 0.348 and 0.596, respectively). In addition, after patients were divided into group A (both cfBRAF^V600E and ltBRAF^V600E positive, n = 56), group B (ltBRAF^V600E positive and cfBRAF^V600E negative, n = 28), and group C (both cfBRAF^V600E and ltBRAF^V600E negative, n = 56), there was a significant difference in the 3-year PFS rate and progression/reactivation rate among the three groups (47.1% ± 7.6%, 92.9% ± 6.1%, and 72.2% ± 6.1%, P < 0.001; 44.6%, 3.6%, and 26.8%, P < 0.001, respectively). In the multivariate analysis, cfBRAF^V600E and age at diagnosis remained independent prognostic factors for 3-year PFS in childhood LCH. Therefore, cfBRAF^V600E was more closely associated with important clinical characteristics, treatment response at week 6, and prognosis than ltBRAF^V600E.

GAS6 signaling tempers Th17 development in patients with multiple sclerosis and helminth infection

Multiple sclerosis (MS) is a highly disabling neurodegenerative autoimmune condition in which an unbalanced immune response plays a critical role. Although the mechanisms remain poorly defined, helminth infections are known to modulate the severity and progression of chronic inflammatory diseases. The tyrosine kinase receptors TYRO3, AXL, and MERTK (TAM) have been described as inhibitors of the immune response in various inflammatory settings. We show here that patients with concurrent natural helminth infections and MS condition (HIMS) had an increased expression of the negative regulatory TAM receptors in antigen-presenting cells and their agonist GAS6 in circulating CD11b^high and CD4⁺ T cells compared to patients with only MS. The Th17 subset was reduced in patients with HIMS with a subsequent downregulation of its pathogenic genetic program. Moreover, these CD4⁺ T cells promoted lower levels of the co-stimulatory molecules CD80, CD86, and CD40 on dendritic cells compared with CD4⁺ T cells from patients with MS, an effect that was GAS6-dependent. IL-10⁺ cells from patients with HIMS showed higher GAS6 expression levels than Th17 cells, and inhibition of phosphatidylserine/GAS6 binding led to an expansion of Th17 effector genes. The addition of GAS6 on activated CD4⁺ T cells from patients with MS restrains the Th17 gene expression signature. This cohort of patients with HIMS unravels a promising regulatory mechanism to dampen the Th17 inflammatory response in autoimmunity.

Helminths have co-evolved with human civilization, and the rapid exclusion from their environment, in the last few decades, has tremendously affected the immune development and regulation. Moreover, several epidemiological studies have shown an inverse correlation between the exposure of these organisms and the development of autoimmunity in industrialized countries. In this sense, helminth therapy appears to be a promising concept to oppose chronic inflammatory and autoimmune diseases because they are master manipulators of host immunity, albeit the mechanisms remain poorly defined. For this reason, it is essential to decipher the main regulatory pathways to hijack the immune response in the absence of parasite infection. Our research described how helminth infection promotes regulatory mechanisms based on the tyrosine kinase TYRO3, AXL, MERTK (TAM) receptors, and their ligand GAS6 to dampen Th17 development and the inflammatory response in patients with multiple sclerosis (MS), a neurodegenerative autoimmune disorder. We show here that GAS6 plays a critical role in the regulation of pro-inflammatory cytokines, transcriptional programs, and plasticity of IL-17 subset. Our work substantiates the hypothesis that enhancing the TAM axis in a manner similar to helminth infection could be a promising alternative for autoimmune diseases.

An Analytically and Diagnostically Sensitive RNA Extraction and RT-qPCR Protocol for Peripheral Blood Mononuclear Cells

Reliable extraction and sensitive detection of RNA from human peripheral blood mononuclear cells (PBMCs) is critical for a broad spectrum of immunology research and clinical diagnostics. RNA analysis platforms are dependent upon high-quality and high-quantity RNA; however, sensitive detection of specific responses associated with high-quality RNA extractions from human samples with limited PBMCs can be challenging. Furthermore, the comparative sensitivity between RNA quantification and best-practice protein quantification is poorly defined. Therefore, we provide herein a critical evaluation of the wide variety of current generation of RNA-based kits for PBMCs, representative of several strategies designed to maximize sensitivity. We assess these kits with a reverse transcription quantitative PCR (RT-qPCR) assay optimized for both analytically and diagnostically sensitive cell-based RNA-based applications. Specifically, three RNA extraction kits, one post-extraction RNA purification/concentration kit, four SYBR master-mix kits, and four reverse transcription kits were tested. RNA extraction and RT-qPCR reaction efficiency were evaluated with commonly used reference and cytokine genes. Significant variation in RNA expression of reference genes was apparent, and absolute quantification based on cell number was established as an effective RT-qPCR normalization strategy. We defined an optimized RNA extraction and RT-qPCR protocol with an analytical sensitivity capable of single cell RNA detection. The diagnostic sensitivity of this assay was sufficient to show a CD8⁺ T cell peptide epitope hierarchy with as few as 1 × 10⁴ cells. Finally, we compared our optimized RNA extraction and RT-qPCR protocol with current best-practice immune assays and demonstrated that our assay is a sensitive alternative to protein-based assays for peptide-specific responses, especially with limited PBMCs number. This protocol with high analytical and diagnostic sensitivity has broad applicability for both primary research and clinical practice.

CSF1R Is Required for Differentiation and Migration of Langerhans Cells and Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disorder characterized by tissue accumulation of CD1a⁺CD207⁺ LCH cells. In LCH, somatic mutations of the BRAF ^V600E gene have been detected in tissue LCH cells, bone marrow CD34⁺ hematopoietic stem cells, circulating CD14⁺ monocytes, and BDCA1⁺ myeloid dendritic cells (DC). Targeting BRAF ^V600E in clonal Langerhans cells (LC) and their precursors is a potential treatment option for patients whose tumors have the mutation. The development of mouse macrophages and LCs is regulated by the CSF1 receptor (CSF1R). In patients with diffuse-type tenosynovial giant cell tumors, CSF1R inhibition depletes tumor-associated macrophages (TAM) with therapeutic efficacy; however, CSF1R signaling in LCs and LCH has not been investigated. We found through IHC and flow cytometry that CSF1R is normally expressed on human CD1a⁺CD207⁺ LCs in the epidermis and stratified epithelia. LCs that were differentiated from CD14⁺ monocytes, BDCA1⁺ DCs, and CD34⁺ cord blood progenitors expressed CSF1R that was downregulated upon maturation. Immature LCs migrated toward CSF1, but not IL34. Administration of the c-FMS/CSF1R kinase inhibitors GW2580 and BLZ945 significantly reduced human LC migration. In LCH clinical samples, LCH cells (including BRAF ^V600E cells) and TAMs retained high expression of CSF1R. We also detected the presence of transcripts for its ligand, CSF1, but not IL34, in all tested LCH cases. CSF1R and CSF1 expression in LCH, and their role in LC migration and differentiation, suggests CSF1R signaling blockade as a candidate rational approach for treatment of LCH, including the BRAF ^V600E and wild-type forms of the disease.

Circulating CD1c+ myeloid dendritic cells are potential precursors to LCH lesion CD1a+CD207+ cells

Langerhans cell histiocytosis (LCH) is a myeloproliferative disorder that is characterized by the inflammatory lesions with pathogenic CD1a+CD207+ dendritic cells (DCs). BRAFV600E and other somatic activating MAPK gene mutations have been identified in differentiating bone marrow and blood myeloid cells, but the origin of the LCH lesion CD1a+CD207+ DCs and mechanisms of lesion formation remain incompletely defined. To identify candidate LCH CD1a+CD207+ DC precursor populations, gene-expression profiles of LCH lesion CD1a+CD207+ DCs were first compared with established gene signatures from human myeloid cell subpopulations. Interestingly, the CD1c+ myeloid DC (mDC) gene signature was most enriched in the LCH CD1a+CD207+ DC transcriptome. Additionally, the BRAFV600E allele was not only localized to CD1a+CD207- DCs and CD1a+CD207+ DCs, but it was also identified in CD1c+ mDCs in LCH lesions. Transcriptomes of CD1a+CD207- DCs were nearly indistinguishable from CD1a+CD207+ DCs (both CD1a+CD207low and CD1a+CD207high subpopulations). Transcription profiles of LCH lesion CD1a+CD207+ DCs and peripheral blood CD1c+ mDCs from healthy donors were compared to identify potential LCH DC-specific biomarkers: HLA-DQB2 expression was significantly increased in LCH lesion CD1a+CD207+ DCs compared with circulating CD1c+ mDCs from healthy donors. HLA-DQB2 antigen was identified on LCH lesion CD1a+CD207- DCs and CD1a+CD207+ DCs as well as on CD1c+(CD1a+CD207-) mDCs, but it was not identified in any other lesion myeloid subpopulations. HLA-DQB2 expression was specific to peripheral blood of patients with BRAFV600E+ peripheral blood mononuclear cells, and HLA-DQB2+CD1c+ blood cells were highly enriched for the BRAFV600E in these patients. These data support a model in which blood CD1c+HLA-DQB2+ mDCs with activated ERK migrate to lesion sites where they differentiate into pathogenic CD1a+CD207+ DCs.

Targeting T cell malignancies using CAR-based immunotherapy: challenges and potential solutions

Chimeric antigen receptor (CAR) T cell therapy has been successful in treating B cell malignancies in clinical trials; however, fewer studies have evaluated CAR T cell therapy for the treatment of T cell malignancies. There are many challenges in translating this therapy for T cell disease, including fratricide, T cell aplasia, and product contamination. To the best of our knowledge, no tumor-specific antigen has been identified with universal expression on cancerous T cells, hindering CAR T cell therapy for these malignancies. Numerous approaches have been assessed to address each of these challenges, such as (i) disrupting target antigen expression on CAR-modified T cells, (ii) targeting antigens with limited expression on T cells, and (iii) using third party donor cells that are either non-alloreactive or have been genome edited at the T cell receptor α constant (TRAC) locus. In this review, we discuss CAR approaches that have been explored both in preclinical and clinical studies targeting T cell antigens, as well as examine other potential strategies that can be used to successfully translate this therapy for T cell disease.

Pro-inflammatory monocyte profile in patients with major depressive disorder and suicide behaviour and how ketamine induces anti-inflammatory M2 macrophages by NMDAR and mTOR

Background

Depression is a highly prevalent disorder that is one of the leading causes of disability worldwide. Despite an unknown aetiology, evidence suggests that the innate and adaptive immune systems play a significant role in the development and maintenance of major depressive disorder (MDD). The non-competitive glutamatergic N-methyl-D-aspartate receptor (NMDAR) antagonist, (R,S)-ketamine (ketamine), has demonstrated rapid and robust efficacy as an antidepressant when administered at sub-anaesthetic doses.

Methods

Our goal was to characterize the pro-inflammatory profile of patients with MDD by measuring pro-inflammatory cytokines in plasma and circulating monocyte subsets and to understand how ketamine induces an anti-inflammatory program in monocyte and macrophages in vitro and vivo.

Finding

Our results show that patients with MDD without other comorbidities (N = 33) exhibited significantly higher levels of pro-inflammatory IL-12 and IL-6 in plasma and that these cytokines were associated with increased numbers of non-classical (CD11b⁺CD16^brightCD14^neg) monocytes and increased activation state (CD40⁺CD86⁺) of classical monocytes in circulation. Remarkably, we have demonstrated that sub-anaesthetic doses of ketamine programs human monocytes into M2c-like macrophages by inducing high levels of CD163 and MERTK with intermediate levels of CD64 and stimulating mTOR-associated gene expression in vitro. The NMDAR antagonist MK-801, but not the α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antagonist, NBQX, also polarizes macrophages to an M2c-like phenotype, but this phenotype disappears upon mTOR pathway inhibition. Sub-anaesthetic doses (10 mg/kg) of ketamine administration in mice both promote reduction of circulating classical pro-inflammatory monocytes and increase of alternative M2 macrophage subtypes in the spleen and CNS.

Interpretation

Our results suggest an anti-inflammatory property of ketamine that can skew macrophages to an M2-like phenotype, highlighting potential therapeutic implications not only for patients with MDD but also other inflammatory-based diseases.

Funding

This study was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT-FONCYT).

Fratricide-resistant CD1a-specific CAR T cells for the treatment of cortical T-cell acute lymphoblastic leukemia

Relapsed/refractory T-cell acute lymphoblastic leukemia (T-ALL) has a dismal outcome, and no effective targeted immunotherapies for T-ALL exist. The extension of chimeric antigen receptor (CAR) T cells (CARTs) to T-ALL remains challenging because the shared expression of target antigens between CARTs and T-ALL blasts leads to CART fratricide. CD1a is exclusively expressed in cortical T-ALL (coT-ALL), a major subset of T-ALL, and retained at relapse. This article reports that the expression of CD1a is mainly restricted to developing cortical thymocytes, and neither CD34+ progenitors nor T cells express CD1a during ontogeny, confining the risk of on-target/off-tumor toxicity. We thus developed and preclinically validated a CD1a-specific CAR with robust and specific cytotoxicity in vitro and antileukemic activity in vivo in xenograft models of coT-ALL, using both cell lines and coT-ALL patient-derived primary blasts. CD1a-CARTs are fratricide resistant, persist long term in vivo (retaining antileukemic activity in re-challenge experiments), and respond to viral antigens. Our data support the therapeutic and safe use of fratricide-resistant CD1a-CARTs for relapsed/refractory coT-ALL.

[Langerhans cell histiocytosis involving the oral and maxillofacial region: an analysis of 12 cases]

OBJECTIVE

To study the clinical features of Langerhans cell histiocytosis (LCH) involving the oral and maxillofacial region in children.

METHODS

A retrospective analysis was performed for the clinical data of 12 children with LCH involving the oral and maxillofacial region who were hospitalized and treated from September 2012 to September 2017, including clinical manifestations, pathological features, treatment and prognosis.

RESULTS

Of the 12 children, 8 (67%) had multiple system involvement and 7 (58%) had the involvement of organs at risk. Bone was the most common affected site (11 children, 92%), among whom 7 children had the involvement of the mandible. Oral soft tissue involvement manifested as gingival ulcer or hyperplasia in 4 children, loose teeth in 5 children, oral mucosal lesions in 2 children, and nodular lesions in 1 child. Pathological examination showed positive CDla in 11 children and positive CD207, CD68, S-100, and LCA in 12 children. Surgery combined with chemotherapy was the major treatment method, and surgical resection alone was performed for focal lesions. After treatment, 11 children were cured or improved and 1 gave up treatment and was lost to follow-up. No recurrence was observed.

CONCLUSIONS

LCH children with oral and maxillofacial involvement often have the involvement of multiple systems and organs at risk, with the mandible as the most common affected site. These children may also have the involvement of gingiva, oral mucosa and teeth. Surgery combined with chemotherapy is the major treatment method, and the patients generally have a good prognosis without recurrence.

Altered Populations of Unconventional T Cell Lineages in Patients with Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) lesions are defined by the presence of CD1a⁺/CD207⁺ myeloid cells, but many other immune cells are present including unconventional T cells, which have powerful immunoregulatory functions. Unconventional T cell lineages include mucosal-associated invariant T (MAIT) cells, type I natural killer T (NKT) cells and gamma-delta (γδ) T cells, which are associated with many inflammatory conditions, although their importance has not been studied in LCH. We characterized their phenotype and function in blood and lesions from patients with LCH, and identified a deficiency in MAIT cell frequency and abnormalities in the subset distributions of γδ T cells and NKT cells. Such abnormalities are associated with immune dysregulation in other disease settings and are therefore potentially important in LCH. Our study is the first to recognize alterations to MAIT cell proportions in patients with LCH. This finding along with other abnormalities identified amongst unconventional T cells could potentially influence the onset and progression of LCH, thereby highlighting potential targets for new immune based therapies.