This section explores the bidirectional crosstalk between the microbiome and the host immune system, covering:

• Mechanisms: mucosal barrier function, pattern recognition receptor (PRR) signaling, and metabolite-mediated immune regulation (e.g., SCFAs, tryptophan metabolites, bile acids).

• Disease links: dysbiosis in chronic inflammation, autoimmune diseases, cancer, and neurodegenerative disorders.

• Therapeutic approaches: probiotics, prebiotics, fecal microbiota transplantation, and engineered microbial consortia.

We welcome original research, reviews, and perspectives on molecular mechanisms, translational applications, and therapeutic innovations in microbiome–immune interactions.