ENG and cancer: CD105 <sup>+</sup> fibroblasts supported anti-inflammatory macrophage-mediated suppression of T cell proliferation, whereas CD105 <sup>-</sup> fibroblasts significantly reduced the suppressive effect of anti-inflammatory macrophages on T cell proliferation.<h4>Conclusions</h4>Establishment of a coculture system to dissect the molecular circuits between CD105 <sup>+</sup> fibroblasts and macrophages that drive immunosuppressive macrophage polarization has broad utility in understanding mammary gland development and events that precede cancer initiation.