Gut microbiota–immune system axis

The “Gut microbiota–immune system axis” describes the dynamic, bidirectional communication network between the gut microbial community and the host’s immune system, affecting both local gut and systemic immune responses, and impacting diverse aspects of health and disease[1][2][3][5][6][8][9]. It is not a single molecule or protein; rather, it encompasses a complex system where microbial products (e.g., short-chain fatty acids, tryptophan metabolites, polysaccharides) influence immune cell differentiation, signaling, and function, while immune processes regulate microbial composition and barrier function[2][3][4][5][6]. Disruption of this axis is implicated in diseases such as inflammatory bowel disease, autoimmunity, cancer, infection, and neurodegeneration[1][3][5][7][8]. Therapeutics such as probiotics, prebiotics, and fecal microbiota transplants attempt to restore or beneficially modulate microbiota–immune interactions, but actions are indirect and often generalized to populations or phenotypes rather than to a defined molecular target[7][8]. This axis is recognized more as a physiological system or conceptual framework than as a discrete, targetable molecule or receptor. Key point: This is not a well-defined receptor, molecule, or protein and therefore does not meet the canonical requirements for a "therapeutic target" relevant for drug screening or biomolecular intervention. It should be classified as "Other" for molecular classification and marked as "incorrect" with respect to standard therapeutic target nomenclature.

Other names

Microbiota-immune axisMicrobiota–gut–immune axisGut microbiome–immune system interaction

Modulation of microbial composition to alter immune responses; Production or modification of metabolites (e.g., SCFAs, indoles) influencing immune cell function; Alteration of barrier integrity affecting immune activity