Biology subjects

Mellins, E. D.

Publications and source records attributed to Mellins, E. D..

3 recordsLinked to original sources

bioRxiv2025

Peripheral Complement C4 Protein in Schizophrenia: Association with Gene Copy Number and Immune Cell Subtypes

The lack of disease-modifying treatments for schizophrenia necessitates the exploration of novel aspects of its pathophysiology, including innate immune mechanisms in the periphery. C4 protein activation, associated with the complement cascade of innate immunity, associates with symptoms and predicts outcomes. However, C4 protein activation does not coincide with expected changes to other proteins in the complement cascade, suggesting another source of C4 protein activation. Using a combination of fresh whole blood from ten anonymous donors and a large set of publicly available microarray data, we show, for the first time, that C4 protein is found and expressed primarily in neutrophils and monocytes. Then, we compared the correlation between C4 protein in neutrophils, classical monocytes, plasma and the number of C4A gene copies. We determined the number of C4A genes using digital droplet PCR, C4 protein in neutrophils (15 patients/21 controls) and plasma (30 patients/38 controls) using western blotting, and classical monocytes (30 patients/38 controls) using flow cytometry. We found a moderate positive correlation between the number of C4A gene copies and the amount of C4 protein only in neutrophils and only in the schizophrenia group (Spearmans rho, r = 0.64, p = 0.01, Cohens d [~]1.67). Our results indicate a convergence of innate immunity mechanisms associated with schizophrenia. This novel mechanism of innate immunity in schizophrenia deserves further study to determine whether it could be a useful drug target.

immunology↗

bioRxiv2024

IFNγ-Expressing Myeloid Cells Localize within Lipoproteinosis during Drug-Associated Pulmonary Alveolar Proteinosis occurring in Systemic Juvenile Idiopathic Arthritis

In the United States, approximately one in 1000 children are diagnosed with the autoinflammatory disease, Juvenile Idiopathic Arthritis (JIA). A subset of JIA cases manifests as Systemic JIA (sJIA), which is characterized by joint pain, fevers, rashes, and systemic inflammation. Severe pulmonary complications have not historically been associated with sJIA. Since 2010, inhibitors of interleukin-1 and interleukin 6 (IL-1i/IL-6i) are the recommended course of treatment for sJIA, yet recently studies show evidence of a severe drug hypersensitivity reaction implicating these medications in a subset of those treated. With this reaction, sJIA patients can develop severe lung disease, including pulmonary alveolar proteinosis (PAP). As this drug-associated lung disease has only recently been identified, the etiology of sJIA drug-associated PAP (sJIA-daPAP) is poorly understood. We used multiplexed ion beam imaging by time-of-flight (MIBI-TOF) to define the cellular immune infiltrate and describe pathological features of PAP in sJIA-daPAP patients. We found an enrichment of eosinophils, neutrophils, and M2 macrophages within regions of lipoproteinosis. These enriched subsets all upregulate IFN{gamma} within lipoproteinosis, a signature specific to sJIA-daPAP samples compared to non-sJIA-PAP samples. In a cellular neighborhood analysis, we identified that eosinophils, neutrophils and M2 macrophages frequently co-localize within the same cellular microenvironment, especially in lipoproteinosis regions. Therefore, this spatial coordination may be involved in clearance or persistence of lipoproteinosis in sJIA-daPAP. This study provides a comprehensive overview of sJIA-daPAP immune pathology and suggests cellular mechanisms that drive inflammation in sJIA patients experiencing pulmonary complications associated with delayed drug hypersensitivity during IL-1i/IL-6i treatment.

immunology↗

bioRxiv2020

Quality control of HLA-DR molecules by the lysosomal aspartyl protease, cathepsin D

Major histocompatibility complex class II (MHCII) molecules display peptides on antigen-presenting cells (APCs) for inspection by CD4+ T cells. MHCII surface levels and life span are regulated post-translationally by peptide loading and ubiquitin-dependent lysosomal targeting, but proteases responsible for MHCII protein degradation remain unidentified. Here, we examined the role of aspartyl proteases in MHCII protein degradation and characterised the form of MHCII that is degraded. Exposure of immature monocyte-derived dendritic cells (MoDCs) and KG-1 acute myeloid leukaemia cells to the aspartyl protease inhibitor, pepstatin A (PepA), caused accumulation of human leukocyte antigen (HLA)-DR molecules in intracellular vesicles. Statistically significant PepA effects on MHCII protein expression were also observed in murine APCs. In KG-1 cells, cathepsin D (CatD) was the sole expressed aspartyl protease, and shRNA-mediated knockdown ablated the PepA effect, providing formal proof of CatD involvement. In vitro, CatD initiated specific cleavage of recombinant DR at F54, a site flanking the peptide-binding groove. Immunochemical characteristics of PepA-rescued DR molecules in KG-1 cells were consistent with selective CatD attack on HLA-DR molecules that lack association with the MHCII chaperone, invariant chain, or with stably bound peptide. We propose that CatD has a critical role in the selective lysosomal disposal of mature HLA-DR molecules that have lost, or never acquired, bound peptide, explaining how MHCII protein life span is coupled to peptide loading.

biochemistry↗