Yoshinobu Eishi, MD, PhD, is a physician-scientist specializing in pathology and host–microbe interactions. He obtained his medical degree and PhD in pathology from Tokyo Medical and Dental University (now Institute of Science Tokyo), where he later served as Professor of Pathology before retirement. He subsequently received a PhD in immunology from the John Curtin School of Medical Research, Australian National University. His research has focused on the etiological mechanisms of sarcoidosis, particularly the role of Cutibacterium acnes, granulomatous inflammation, and immunopathological diagnostics, including species-specific immunohistochemistry. He serves as a Guest Editor for the Special Issue “Immune System and Commensal Microbiota” in Microorganisms.