For example, pectin supplementation in CRC patient-derived microbiota-humanized mice enhances anti-PD-1 efficacy by enriching butyrate-producing bacteria (e.g., Faecalibacterium prausnitzii), with butyrate directly recruiting CD8+ T cells to the TME and suppressing Treg differentiation (264). The gene discussed is CD8A; the disease is colorectal carcinoma.