CD4 and neoplasm: Once cancer is established, microorganisms can infiltrate the tumor microenvironment (TME), working synergistically with tumor-infiltrated leukocyte subpopulations (LSPs); tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), CD4+CD25+Foxp3+Tregs creating a robust and strong immunosuppressive barrier (37, 87, 222, 223).