CD4 and breast cancer: IL-17 was also found to control neutrophil recruitment in lung metastasis of BC in a mouse model: CD3+CD4+ and γδ T cells were the major sources of IL-17 (70, 71), and it was interesting to find that the absence of γδ T cells or neutrophils markedly reduced pulmonary and lymph node metastases without influencing primary tumor progression, which suggested a collaborative relationship between γδ T cells and neutrophils in promoting BC lung metastasis.