Interpheron type II signature in mucosal swabs of patient with infantile colic treated with Limosilactobacillus reuteri (L. reuteri) LMG P-27481

Purpose: Infantile colic is increasingly linked to gut microbiota alterations and immune dysregulation, characterized by an imbalance between pro-inflammatory and regulatory pathways. While Lactobacillus reuteri DSM17938 reduces crying time in colicky infants, its immunological mechanisms remain unclear. This study investigated the modulation of type II interferon-stimulated genes (ISGs) in the oral mucosa of colicky infants treated with L. reuteri LMG P-27481 to better understand its impact on mucosal and systemic immunity. Patients and Methods: Infants with colic were randomized to receive L. reuteri LMG P-27481 or placebo. Type II interferon signature analysis was performed using Real-Time PCR to quantify ISG expression in the oral mucosa. The genes analysed included CXCL9, IDO1, HLA-DRA, STAT1, and CXCL10. FABP4 was used to confirm treatment-related changes, and expression was compared between groups. Results: L. reuteri administration significantly upregulated CXCL9, IDO1, and HLA-DRA compared to placebo. CXCL9 is involved in immune cell recruitment, suggesting enhanced local immune surveillance. IDO1 upregulation indicates a shift towards immune tolerance through tryptophan metabolism, potentially reducing mucosal hyperreactivity. Increased HLA-DRA expression implies improved antigen presentation capacity, contributing to balanced immune regulation. These findings suggest that L. reuteri modulates mucosal immunity beyond the gastrointestinal tract. Conclusion: L. reuteri LMG P-27481 influences immune gene expression in the oral mucosa of colicky infants, supporting its role in promoting immune homeostasis. This immunomodulatory effect may complement its known action on gut microbiota, offering new therapeutic perspectives for infant colic and other pediatric inflammatory conditions. Further research is needed to assess the strain-specificity of these effects and their long-term implications.