CD8A and neoplasm: When looking at host immunity at a systemic level in the same patient cohort, it was found that patients with abundant Faecalibacterium, Ruminococcaceae and Clostridiales had increased systemic circulation levels of CD4+ and CD8+ T cells and a greater cytokine response to anti-PD-1, whereas those with abundant Clostridiales had higher levels of regulatory T cells and myeloid-derived suppressor cells and a reduced cytokine response to anti-PD-1, suggesting that the gut microbiota was not only capable of modulating the host anti-tumour response at the TME level, but also at the systemic level.