CD4 and breast carcinoma: On the other hand, in terms of the effect of ECM on TH cells in the TME, a study (48) found that the elimination of FAP+ CAFs in vivo can implement the polarization of TH2 cells to TH1 cells; moreover, in breast cancer, the CAF1-S1 subtype could achieve immunosuppression by recruiting and increasing the differentiation of CD4+CD25+ Treg (49).