A study on MCA205 sarcoma cell lines reported that specific monoclonal antibodies anti-CTLA-4 controlled tumor progression, but the facilitation of the immunological response was expanded specifically in specific pathogen-free mice, not in germ-free ones or in others treated with broad-spectrum antibiotics, due to decreased activation of splenic CD4+ T cells and tumor-infiltrating lymphocytes [36]. This evidence concerns the gene CD4 and neoplasm.