CD4 and breast cancer: However, CD4+ T cell transfer into Tslp-PyMttg Rag1KO reconstituted breast cancer protection in these animals, as shown by significantly delayed tumor onset (P < 0.0001; Fig. 1 I), fewer tumors (P < 0.05; Fig. 1 J), and markedly increased survival compared with PyMttg Rag1KO mice that received CD4+ T cells (P < 0.0001; Fig. 1 K).