We further used Rag1−/− mice, anti‐CD8 neutralizing antibody, and adoptive cell transfer therapy to validate the sensitizing immunotherapeutic effects of L. johnsonii and its derived IPA dependent on CD8+ T cells, and sorted CD8+ T cells infiltrated in tumours of mice for single‐cell RNA sequencing (scRNA‐seq), single‐cell TCR sequencing (scTCR‐seq) and single‐cell assay for targeting accessible‐chromatin with high‐throughout sequencing (scATAC‐seq). The gene discussed is CD8A; the disease is neoplasm.