Biology subjects

Howlett, S. K.

Publications and source records attributed to Howlett, S. K..

4 recordsLinked to original sources

bioRxiv2024

The immunological profile of RC17 hESC-derived dopaminergic neural progenitor cells in vitro: implications for the STEM-PD clinical trial.

Parkinsons Disease involves the progressive loss of dopaminergic neurons (DAn), prompting clinical trials replacing cell loss with neural grafts. This includes the transplantation of pluripotent stem cell-derived DAn progenitor cells (NPC) currently under investigation in the STEM-PD trial. To determine the likelihood of immune rejection post-grafting, we characterised the immunogenicity of the STEM-PD product (RC17-hESC-derived NPCs), comparing them to human foetal ventral mesencephalic tissue (hfVM) previously tested in trials, including our own TRANSEURO trial. Despite MHC-Class I expression, upregulated by proinflammatory cytokines, no immune response to NPCs was detected in vitro. Instead, they were immunosuppressive. Transcriptomic analysis revealed similarities between RC17-NPCs and hfVM, both strongly upregulating antigen processing and presentation pathways in response to IFN{gamma}. Furthermore, immunosuppressant mycophenolate mofetil detrimentally affected NPC survival and differentiation in vitro. Overall, our data suggest that aggressive immunosuppression is not required following hESC-NPC transplantation and that caution should be exercised when selecting the immunosuppressive regimen.

neuroscience↗

bioRxiv2024

Multimodal profiling reveals tissue-directed signatures of human immune cells altered with age

The immune system comprises multiple cell lineages and heterogeneous subsets found in blood and tissues throughout the body. While human immune responses differ between sites and over age, the underlying sources of variation remain unclear as most studies are limited to peripheral blood. Here, we took a systems approach to comprehensively profile RNA and surface protein expression of over 1.25 million immune cells isolated from blood, lymphoid organs, and mucosal tissues of 24 organ donors aged 20-75 years. We applied a multimodal classifier to annotate the major immune cell lineages (T cells, B cells, innate lymphoid cells, and myeloid cells) and their corresponding subsets across the body, leveraging probabilistic modeling to define bases for immune variations across donors, tissue, and age. We identified dominant tissue-specific effects on immune cell composition and function across lineages for lymphoid sites, intestines, and blood-rich tissues. Age-associated effects were intrinsic to both lineage and site as manifested by macrophages in mucosal sites, B cells in lymphoid organs, and T and NK cells in blood-rich sites. Our results reveal tissue-specific signatures of immune homeostasis throughout the body and across different ages. This information provides a basis for defining the transcriptional underpinnings of immune variation and potential associations with disease-associated immune pathologies across the human lifespan.

immunology↗

bioRxiv2023

Hiding in Plain Sight: Thymic CD8+FOXP3+Tregs sequester CD25 and are enriched in human tissues

For decades, regulatory T cell (Treg) research has focussed on CD4+FOXP3+ Tregs, while characterisation of CD8+FOXP3+ Tregs has been limited due to their scarcity in blood. Here, by analysing 95 tissue samples from 26 deceased transplant organ donors we show that, despite representing less than 5% of circulating Tregs, CD8+ Tregs are enriched in human tissue, particularly in non-lymphoid tissues and bone marrow. We further show that they are fully demethylated at the FOXP3 TSDR, indicating lineage stability, and demonstrate their presence in human thymic tissue and cord blood. Transcriptomic profiling revealed strong similarities to CD4+ Tregs, however at the protein level, they reside in tissue as surface CD25lo/-CD8+CD69+CD103+TLR9+HELIOS+FOXP3+ cells, expressing CD25 intracellularly. Surface CD25 was rapidly regained ex-vivo, allowing us to sort and expand them, and to subsequently demonstrate their therapeutic potential in a humanised mouse model of graft-vs-host disease. Additionally we report increased circulating CD8+Tregs in individuals with SLE and patients early following traumatic brain injury (TBI), underscoring their functional importance. We conclude that these under-studied cells likely play an essential but previously unappreciated role in maintaining peripheral tolerance. One Sentence SummaryFOXP3+CD8+ Tregs, expressing tissue residency markers and intracellular CD25, are enriched in human non-lymphoid tissues.

immunology↗

bioRxiv2023

FlowAtlas.jl: an interactive tool bridging FlowJo with computational tools in Julia

As the dimensionality, throughput, and complexity of cytometry data increases, so does the demand for user-friendly, interactive analysis tools that leverage high-performance machine learning frameworks. Here we introduce FlowAtlas.jl: an interactive web application that bridges the user-friendly environment of FlowJo and computational tools in Julia developed by the scientific machine learning community. We demonstrate the capabilities of FlowAtlas using a novel human multi-tissue, multi-donor immune cell dataset, highlighting key immunological findings.

bioinformatics↗