Phenotypic and transcriptional analysis of stromal cells in pancreatic lymph nodes in Type 1 diabetes

BACKGROUND: Antigen-presenting cell (APC) populations in pancreatic lymph nodes (PLNs) remain poorly defined, and whether phenotypic or functional alterations in these populations contribute to the imbalance in T cell responses in human PLNs is yet to be determined. Furthermore, alternative APC subsets that maintain a tolerogenic phenotype in this tissue may constitute new putative targets to explore for antigen-specific therapy. Our aim is to compare the phenotype of dendritic and stromal cell subsets from the PLNs of Type 1 diabetes (T1D) and control donors (as well as between NOD and NOR mice), as well as the transcriptional profile of selected tolerance-related genes. We hypothesize that impaired tolerance in T1D might in part associated with alterations in tolerogenic functions of APCs.

METHODS: We analyzed the phenotype of different dendritic and stromal cell subsets from the PLNs of T1D and control donors by flow cytometry, as well as the expression of 44 tolerance-related genes and beta-cell antigens in sorted APC subsets using the BioMark qPCR platform. As little is known about stromal cells in T1D, we also compared the phenotype of these cells between NOD and NOR mice in different lymph nodes at different stages of disease.

RESULTS: Differences in phenotypic markers emerged between dendritic and stromal cell subsets and between T1D and control donors. A subset of stromal cells was found reduced in relative abundance, while HLA-DR and PD-L1 were upregulated on the major stromal cell populations. Although interesting differences were also seen between NOD and NOR mice, these only partially recapitulated the observations made in human PLNs, suggesting potential differences in the PLN environment and how these cells contribute or respond to disease-related signals. The expression of some beta-cell antigens, transcription factors and cytokines seems to be differently regulated among subsets of stromal cells and between control and T1D samples.