CD4 and neoplasm: More sophisticated models using RAG2/γc deficient mice, which lack all lymphocytes including NK, iNKT, γδ T, classical CD4+ and CD8+ αβ T cells and B cells, showed a higher incidence of tumor growth compared to RAG2 deficient mice alone (which lack αβ T cells and B cells) demonstrating that indeed NK cells are in part responsible for inhibiting tumor growth (20).