The finding that ErbB4 signaling in macrophages leads to cell death might seem unexpected, as previous studies with non-transformed cells have largely defined a pro-survival role for this receptor.19, 44, 45 However, an apoptotic response to ErbB4 in breast cancer cells has been previously observed, and our findings in macrophages may involve a similar mechanism. Here, ERBB4 is linked to breast carcinoma.