Digestive tract microflora liberates low molecular weight peptides with immunotriggering activity.

Antibiotic digestive tract decontamination in BALB/c-mice resulted in a significant reduction of peritoneal macrophage function and lymphocyte proliferation. Considerable evidence has accumulated showing that certain species of the indigenous gastrointestinal (GI)-tract microflora, e.g. Bacteroides sp., Clostridium sp., Lactobacillus sp., and Propionibacterium sp., liberate low molecular weight peptides which are able to trigger basic immune responses. Eradication of the GI-tract microflora apparently results in a lack of peptide production correlating to immunosuppression in experimental BALB/c-mice. Substitution of peptides in GI-tract decontaminated mice reconstituted macrophage function as well as proliferation of lymphatic tissue.