Abnormalities in T cell lineages from patients with Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare inflammatory disease characterised by lesions containing CD1a+ myeloid lineage ‘LCH’ cells. Other immune cells such as T cells are also present within LCH lesions and the cytokine milieu suggests T cell activation. T cells have an established role in regulating cellular immunity and there is already evidence that multiple T cell lineages are enriched in LCH lesions, implying that they may have a role in LCH pathogenesis. Foxp3+ regulatory T cells (Tregs) and the immune suppressive cytokine, transforming growth factor beta (TGF-Doctor of Philosoph

Patients with both langerhans cell histiocytosis and crohn’s disease highlight a common role of interleukin-23

Aim: To present the first case series of patients with Langerhans cell histiocytosis (LCH) also affected by Crohn's disease (CD), both of which are granulomatous diseases, and in LCH investigate the role of interleukin (IL)-23, which is a well-described disease mediator in CD. Methods: A case series of three patients with LCH and CD were described; a cohort of LCH patients (n = 55) as well as controls (n = 55) were analysed for circulating IL-23 levels; and the relation between the percentage of LCH cells in lesions and circulating IL-23 levels was analysed in seven LCH patients. Results: Differential diagnostic challenges for these two granulomatous diseases were highlighted in the case series, and it took up to 3 years to diagnose CD. Elevated IL-23 levels were found in LCH patients. The amount of lesional LCH cells correlated with the levels of circulating IL-23. Conclusion: Both CD and LCH should be considered in patients with inflammatory gastrointestinal involvement. The IL-23 pathway is a common immunological trait between these two granulomatous diseases. ©2020 The Authors. Acta Paediatrica published by John Wiley & Sons Ltd on behalf of Foundation Acta Paediatrica. ***Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Jenée Mitchell” is provided in this record**

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. Copyright © 2022 Mitchell, Kvedaraite, von Bahr Greenwood, Lourda, Henter, Berzins and Kannourakis

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

Foxp3+ tregs from langerhans cell histiocytosis lesions co-express CD56 and have a definitively regulatory capacity

Langerhans cell histiocytosis (LCH) lesions contain myeloid lineage ‘LCH’ cells. Regulatory T cells (Tregs) are also enriched within lesions, although their role in LCH pathogenesis is unknown. LCH cells are thought to produce the transforming growth factor beta (TGF-β) within lesions, however whether Tregs contribute is unestablished. Using flow cytometry, we analyzed relative frequencies of live Tregs from LCH patients and identified CD56 expression and TGF-β production by lesion Tregs. While CD56+ Tregs were enriched in lesions, overall CD56+ T cells were reduced in the blood from active LCH patients compared to non-active disease patients, and there was a negative correlation between CD8+CD56+ T cells and Tregs. We propose that inducing a Treg phenotype in T cells such as CD56+ T cells may be a mechanism by which LCH cells divert inflammatory T cell responses. Thus, Tregs within LCH lesions are likely an important component in LCH pathogenesis. © 202

Polyclonal T-Cells Express CD1a in Langerhans Cell Histiocytosis (LCH) Lesions

Langerhans cell histiocytosis (LCH) is a complex and poorly understood disorder that has characteristics of both inflammatory and neoplastic disease. By using eight-colour flow cytometry, we have identified a previously unreported population of CD1a+/CD3+ T-cells in LCH lesions. The expression of CD1a is regarded as a hallmark of this disease; however, it has always been presumed that it was only expressed by pathogenic Langerhans cells (LCs). We have now detected CD1a expression by a range of T-cell subsets within all of the LCH lesions that were examined, establishing that CD1a expression in these lesions is no longer restricted to pathogenic LCs. The presence of CD1a+ T-cells in all of the LCH lesions that we have studied to date warrants further investigation into their biological function to determine whether these cells are important in the pathogenesis of LCH.[ABSTRACT FROM AUTHOR

Expression of CD1a and CD3 mRNA in CD1a⁺/CD3⁺ cells sorted by FACS from LCH lesions.

<p>(A) Plot showing anti-CD1a-FITC [NA 1/34] and anti-CD3-APC-H7 [SK7] staining of LCH lesional cells from patient #1 by flow cytometry. The boxed area shows the gate used to sort CD1a⁺/CD3⁺ cells. This plot is representative for all patients examined. RNA was extracted from the CD1a⁺/CD3⁺ sorted cells and reverse transcribed for PCR amplification. (B) Agarose gel electrophoresis of RT-PCR products generated using primers specific for CD1a, CD3 and β-actin. PCR was initially performed with sorted cells from patient #1 and was later performed with sorted cells from patients #3, #4 and #6. PCR was not possible on sorted cells from patients #2 and #5. The positive control (+ve) was a cDNA sample previously shown to contain the amplicon and the negative control (-ve) was a reaction with no cDNA added.</p

Experimental details for control patients.

<p>Experimental details for control patients.</p

CD1a expression on T-cells is not restricted to either CD4⁺ or CD8⁺ subsets.

<p>The flow cytometry plots are from one experiment using lesional cells from LCH patient #1. Live cells were gated into quadrants based upon CD1a and CD3 antibody intensity and the percentages of cells were calculated. Live cells are defined as those cells remaining after doublet and propidium iodide positive cells were excluded. CD1a⁺/CD3⁺ cells were then gated to identify CD1a⁺/CD3⁺/CD4⁺ cells and CD1a⁺/CD3⁺/CD8⁺ cells. Similarly, CD1a^−/CD3⁺ cells were gated to identify CD1a^−/CD3⁺/CD4⁺ cells and CD1a^−/CD3⁺/CD8⁺ cells. Plots show staining for anti-CD1a-APC [HI149], anti-CD3-APC-H7 [SK7], anti-CD4-V450 [RPA-T4] and anti-CD8-PE [HIT8a].</p

Percentage of CD1a⁺ T-cells that express additional CD markers.

<p>Percentage of CD1a⁺ T-cells that express additional CD markers.</p