|WIARDA, JAYNE - Oak Ridge Institute For Science And Education (ORISE)
|SIVASANKRAN, SATHESH - Iowa State University
Submitted to: International Veterinary Immunology Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 9/11/2023
Publication Date: N/A
Technical Abstract: Macrophage subsets and their varying functions in pig intestine are ill-defined despite important roles of macrophages in intestinal immune induction and homeostasis. Single-cell RNA sequencing of porcine jejunum and ileum containing Peyer’s patches was performed to identify porcine intestinal macrophage subsets, inferred functional differences via biological process enrichment analysis of differentially expressed genes, and signaling networks between cellular subsets. Macrophages were divided into two major subsets based on expression of CD4. CD4+ macrophages had gene expression indicative of activation, phagocytosis, inflammation, cytotoxicity, cellular catalysis, and cell receptor signaling. Genes expressed by CD4- macrophages indicated roles in translation, cell motility, and locomotion. Thus, gene expression profiles indicated different functions for macrophage subsets in the pig intestine based on CD4 expression. In situ staining revealed macrophages surround and infiltrate B cell-rich Peyer’s patch follicles, suggesting close proximity of macrophages to B cells might promote macrophage-B cell signaling. Signaling networks inferred from cell subset gene expression indicated macrophages were major recipients of B cell-derived cues via cell-cell contact and secreted signaling. However, the majority of B cell-derived signals were directed at CD4+ rather than CD4- macrophages, including inferred interactions between B cell-expressed MHC-II and macrophage-expressed CD4. Results indicate porcine intestinal macrophages are functionally distinguishable by expression of CD4 and further suggest CD4+ macrophages perform biological functions as cytotoxic, phagocytic, effector cells in response to B cell-derived signals. Predicted effector functions and responsiveness to B cells for porcine intestinal CD4+ macrophages are similar to described roles of CD4+ macrophages in humans, including tingible-body macrophages that clear apoptotic B cells and other CD4+ macrophage subsets that are maintained as resident effector cells. Altogether, results provide a newly-defined signaling axis and appreciation of macrophage heterogeneity in porcine small intestine that can be further applied to understand context and dynamics of intestinal immune status.