CTLA4 and neoplasm: Within CD45+ immune compartments of both OSCC (DSP cohort 1; n = 8 patients) and CRC (DSP cohort 2; n = 10 patients) tumours, we independently show that bacteria reside in highly immunosuppressive microniches that are characterized by an enrichment of mature CD66b+ myeloid cells along with an upregulation of the immunosuppressive molecule ARG1 (arginase 1) and the immune checkpoint protein CTLA4 (cytotoxic T-lymphocyte-associated protein 4) (Fig. 2b).