Abstract
The participating signals and structures that enable primary immune cells migrating within dense tissues are not completely revealed until now. Especially in autoimmune diseases, mostly unknown mechanisms facilitate autoreactive immune cells to migrate to endogenous tissues, infiltrating and harming organ-specific structures. In order to gain deeper insights into the migratory behavior of primary autoreactive immune cells, we examined peripheral blood-derived lymphocytes (PBLs) of horses with equine recurrent uveitis (ERU), a spontaneous animal model for autoimmune uveitis in humans. In this study, we used a three-dimensional collagen I hydrogel matrix and monitored live-cell migration of primary lymphocytes as a reaction to different chemoattractants such as fetal calf serum (FCS), cytokines interleukin-4 (IL-4), and interferon-γ (IFN-γ), and a specific uveitis autoantigen, cellular retinaldehyde binding protein (CRALBP). Through these experiments, we uncovered distinct differences between PBLs from ERU cases and PBLs from healthy animals, with significantly higher cell motility, cell speed, and straightness during migration of PBLs from ERU horses. Furthermore, we emphasized the significance of expression levels and cellular localization of septin 7, a membrane-interacting protein with decreased abundance in PBLs of autoimmune cases. To underline the importance of septin 7 expression changes and the possible contribution to migratory behavior in autoreactive immune cells, we used forchlorfenuron (FCF) as a reversible inhibitor of septin structures. FCF-treated cells showed more directed migration through dense tissue and revealed aberrant septin 7 and F-actin structures along with different protein distribution and translocalization of the latter, uncovered by immunochemistry. Hence, we propose that septin 7 and interacting molecules play a pivotal role in the organization and regulation of cell shaping and migration. With our findings, we contribute to gaining deeper insights into the migratory behavior and septin 7-dependent cytoskeletal reorganization of immune cells in organ-specific autoimmune diseases.
Highlights
The research on mechanisms and motives of cells to migrate to inflammation sites through tissues and endothelial barriers is of major interest for immunologists
We investigated migration parameters of primary lymphocytes (Supplemental Figure 1) as well as the role of septin 7 and F-actin, which possibly participate and promote migration of respective cells
Our initial findings on migratory behavior showed that peripheral blood-derived lymphocytes (PBLs) of equine recurrent uveitis (ERU) cases migrated greater distances and moved significantly faster through dense collagen matrix compared to PBLs of healthy animals, increasing their cell speed by up to 29% (Figures 1–4)
Summary
The research on mechanisms and motives of cells to migrate to inflammation sites through tissues and endothelial barriers is of major interest for immunologists. Besides highly agile innate immune cells such as neutrophils, which act as the first line of defense at the site of inflammation (Goldberg et al, 2016), T lymphocytes are able to achieve high-speed movements (Miller et al, 2002; Katakai and Kinashi, 2016). The exact mechanisms that enable T cells to reach high cell speed and directed migration even within dense tissue environments, are still elusive. The unique ameboid migration of leukocytes through dense tissue, pursuing the path of least resistance, was described to be facilitated by nuclear positioning and the ability to adapt to the physical constraints of their surrounding environment (Renkawitz et al, 2019). The correlation between the cell’s actin-cytoskeleton and interacting proteins plays a pivotal role during cell migration (Tooley et al, 2009; Dupré et al, 2015)
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