B cell immune profiles in dysbiotic vermiform appendixes of pancreatic cancer patients

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest solid tumors and is resistant to immunotherapy. B cells play an essential role in PDAC progression and immune responses, both locally and systemically. Moreover, increasing evidence suggests that microbial compositions inside the tumor, as well as in the oral cavity and the gut, are important factors in shaping the PDAC immune landscape. However, the gut-associated lymphoid tissue (GALT) has not previously been explored in PDAC patients. In this study, we analyzed healthy vermiform appendix (VA) from 20 patients with PDAC and 32 patients with colon diseases by gene expression immune profiling, flow cytometry analysis, and microbiome sequencing. We show that the VA GALT of PDAC patients exhibits markers of increased inflammation and cytotoxic cell activity. In contrast, B cell function is decreased in PDAC VA GALT based on gene expression profiling; B cells express significantly fewer MHC class II surface receptors, whereas plasma cells express the immune checkpoint molecule HLA-G. Additionally, the vermiform appendix microbiome of PDAC patients is enriched with Klebsiella pneumoniae, Bifidobacterium animalis, and Adlercreutzia equolifaciens, while certain commensals are depleted. Our findings may suggest impaired B cell function within the GALT of PDAC patients, which could potentially be linked to microbial dysbiosis. Additional investigations are imperative to validate our observations and explore these potential targets of future therapies.

Virus-specific TRM cells of both donor and recipient origin reside in human kidney transplants

Tissue-resident lymphocytes (TRLs) are critical for local protection against viral pathogens in peripheral tissue. However, it is unclear if TRLs perform a similar role in transplanted organs under chronic immunosuppressed conditions. In this study, we aimed to characterize the TRL compartment in human kidney transplant nephrectomies and examine its potential role in antiviral immunity. The TRL compartment of kidney transplants contained diverse innate, innate-like, and adaptive TRL populations expressing the canonical residency markers CD69, CD103, and CD49a. Chimerism of donor and recipient cells was present in 43% of kidney transplants and occurred in all TRL subpopulations. Paired single-cell transcriptome and T cell receptor (TCR) sequencing showed that donor and recipient tissue-resident memory T (TRM) cells exhibit striking similarities in their transcriptomic profiles and share numerous TCR clonotypes predicted to target viral pathogens. Virus dextramer staining further confirmed that CD8 TRM cells of both donor and recipient origin express TCRs with specificities against common viruses, including CMV, EBV, BK polyomavirus, and influenza A. Overall, the study results demonstrate that a diverse population of TRLs resides in kidney transplants and offer compelling evidence that TRM cells of both donor and recipient origin reside within this TRL population and may contribute to local protection against viral pathogens.

Mast Cells in Kidney Transplant Biopsies With Borderline T Cell-mediated Rejection and Their Relation to Chronicity

Mast cells are potential contributors to chronic changes in kidney transplants (KTx). Here, the role of mast cells (MCs) in KTx is investigated in patients with minimal inflammatory lesions.

Methods

Fourty-seven KTx biopsies (2009-2018) with borderline pathological evidence for T cell-mediated rejection according to the Banff'17 Update were retrospectively included and corresponding clinical data was collected. Immunohistochemistry for tryptase was performed on formalin-fixed paraffin-embedded sections. Cortical MCs were counted and corrected for area (MC/mm²). Interstitial fibrosis was assessed by Sirius Red staining and quantified using digital image analysis (QuPath).

Results

Increased MC number was correlated to donor age (spearman's r = 0.35, P = 0.022), deceased donor kidneys (mean difference = 0.74, t [32.5] = 2.21, P = 0.035), and delayed graft function (MD = 0.78, t [33.9] = 2.43, P = 0.020). Increased MC number was also correlated to the amount of interstitial fibrosis (r = 0.42, P = 0.003) but did not correlate with transplant function over time (r = -0.14, P = 0.36). Additionally, transplant survival 2 y post-biopsy was not correlated to MC number (mean difference = -0.02, t [15.36] = -0.06, P = 0.96).

Conclusions

MC number in suspicious (borderline) for acute T cell-mediated rejection is correlated to interstitial fibrosis and time post-transplantation, suggesting MCs to be a marker for cumulative burden of tissue injury. There was no association between MCs and transplant function over time or transplant survival 2 y post-biopsy. It remains unclear whether MCs are just a bystander or have pro-inflammatory or anti-inflammatory effects in the KTx with minimal lesions.

Extracellular Matrix Analysis of Human Renal Arteries in Both Quiescent and Active Vascular State

In vascular tissue engineering strategies, the addition of vascular-specific extracellular matrix (ECM) components may better mimic the in vivo microenvironment and potentially enhance cell-matrix interactions and subsequent tissue growth. For this purpose, the exact composition of the human vascular ECM first needs to be fully characterized. Most research has focused on characterizing ECM components in mature vascular tissue; however, the developing fetal ECM matches the active environment required in vascular tissue engineering more closely. Consequently, we characterized the ECM protein composition of active (fetal) and quiescent (mature) renal arteries using a proteome analysis of decellularized tissue. The obtained human fetal renal artery ECM proteome dataset contains higher levels of 15 ECM proteins versus the mature renal artery ECM proteome, whereas 16 ECM proteins showed higher levels in the mature tissue compared to fetal. Elastic ECM proteins EMILIN1 and FBN1 are significantly enriched in fetal renal arteries and are mainly produced by cells of mesenchymal origin. We functionally tested the role of EMILIN1 and FBN1 by anchoring the ECM secreted by vascular smooth muscle cells (SMCs) to glass coverslips. This ECM layer was depleted from either EMILIN1 or FBN1 by using siRNA targeting of the SMCs. Cultured endothelial cells (ECs) on this modified ECM layer showed alterations on the transcriptome level of multiple pathways, especially the Rho GTPase controlled pathways. However, no significant alterations in adhesion, migration or proliferation were observed when ECs were cultured on EMILIN1- or FNB1-deficient ECM. To conclude, the proteome analysis identified unique ECM proteins involved in the embryonic development of renal arteries. Alterations in transcriptome levels of ECs cultured on EMILIN1- or FBN1-deficient ECM showed that these candidate proteins could affect the endothelial (regenerative) response.

Abstract 2348: Expression of CECR1 by activated M2-type macrophages in glioma

Objectives

Glial neoplasms harbor macrophages which are mainly of the M2 type and secrete Th2 cytokines. These M2 macrophages are not only involved in immune suppression but also serve functions in angiogenesis. Recent studies have shown that the adenosine deaminase CECR1 is involved in the maintenance of vascular homeostasis and M2-macrophage differentiation. Here we aim to identify the expressional levels of CECR1 in M1 and M2 macrophage populations in gliomas and investigate the role of these cells in glioma development.

Methods

To identify the relation between CECR1 expression and the macrophage subtypes, tissue samples of human glioma and normal brain controls were used for Real Time PCR and immunostaining. For in vitro functional studies, we generated M1 and M2-like macrophages by differentiating CD14+ monocytes isolated from human peripheral blood in GM-CSF and M-CSF medium. With and without stimulation of GBM conditioned medium, CECR1 level was measured by RT-PCR and western blot. CECR1 protein was added to the macrophage culture medium and the expression level of the M1 marker CD80 and the M2 marker CD163 were measured by flow cytometry and confocal microscopy.

Results

The macrophages were predominantly present in perivascular spaces, but also in the tumor tissue and neuropil of the normal brain. At the mRNA level the expression of CECR1 was positively correlated with the M2 markers CD204 and IL-10. Immunohistochemical investigation revealed that CECR1 is localized in microglia and macrophages in low-grade gliomas and control brain and it overlaps and co-localizes with the M2-markers CD204 and CD163, but not the M1-marker CD80. In vitro experiments showed that CECR1 expression is higher in the M-CSF-induced M2-macrophages than in their GM-CSF-induced M1 counterparts. Under the stimulation of GBM conditioned medium, increased CECR1 is detected in both M1 and M2-like macrophages. In addition, exogenous CECR1 greatly affects both M-CSF and GM-CSF induced macrophages’ response by up-regulating CD163 in M1-like macrophages and increasing CD163 positive cells in M2-like macrophages. As a result, CECR1 skews macrophage differentiation towards the M2 phenotype.

Conclusion

This study is the first to show that the M2-macrophage, not the M1-macrophage in glioma, is the main source of CECR1. In addition, CECR1 is shown to be a potent regulator of M2-macrophages. High levels of CECR1 is able to skew GM-CSF driven M1 macrophage differentiation towards an M2 macrophage phenotype. We propose that CECR1 expression by macrophages promotes M2-macrophage differentiation under the influence of an adenosine-rich glioma microenvironment to support tumor growth and tumor angiogenesis. The findings may well direct the search for new anti-angiogenic target molecules for the treatment of glioma.

Citation Format: Changbin Zhu, Marcel M. van der Weiden, Adrea Scchetti, Thierry P.P. van den Bosch, Ihsan Chrifi, Maarten M. Brandt, Dana A.M. Mustafa, Caroline Cheng, Johan M. Kros. Expression of CECR1 by activated M2-type macrophages in glioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2348. doi:10.1158/1538-7445.AM2015-2348