In this podcast, Dr Davar starts by providing a background on the importance of the microbiome in adaptive and innate immunity, while Dr Spencer states the importance of the cross-talk between the microbiome and immune system through microbial products, peptides, and metabolites. Dr Davar then explains the concept of immunosurveillance, immunoediting, and checkpoint inhibitors. Dr Spencer describes fecal microbiome transplant studies that showed features of the microbiome can predict response to immunotherapy and effect T-cell expression. Dr Davar then describes some of the studies that are looking at fecal microbiome transplant in combination with checkpoint inhibitors. He goes on to discuss studies investigating the use of live bacterial products to elicit the same effects as fecal microbiome transplant, particularly the mediation of CD8 T cells. Dr Spencer also talks about probiotics, antibiotics, and diet and explains how this can affect the gut microbiome and describes studies looking at these features in terms of response to immunotherapies. She also describes the microbiome research related to graft-versus-host-disease and the impact of higher alpha diversity on post-transplant survival, while Dr Davar explains how the microbiome may also affect toxicity and side-effects of cancer immunotherapies.