Recolonization experiments of previously antibiotic-treated SPF mice or GF mice with specific bacterial isolates from the small intestinal mucosa of SPF mice also showed that introduction of Bacteroides fragilis, Bacteroides thetaiotaomicron, Burkholderia cepacia, or the combination of B. fragilis and B. cepacia led to restoration of anti-CTLA-4 antibody-mediated anti-tumor responses [24]. This evidence concerns the gene CTLA4 and neoplasm.