L. reuteri produces I3A

One specific strain, Lactobacillus reuteri, has been found to stimulate the function of killer T cells by producing a compound called indole-3-aldehyde (I3A). When the mice were fed a diet rich in tryptophan, an amino acid that L. reuteri produces I3A, immunotherapy drugs showed an enhanced efficacy in reducing tumor size and extending mice's survival rate.