Tissue-resident macrophages form an essential part of the first line of defense in all tissues
of the body. Next to their immunological role, they play an important role in maintaining
tissue homeostasis. Recently, it was shown that they are primarily of embryonic origin.
During embryogenesis, precursors originating in the yolk sac and fetal liver colonize the
embryonal tissues where they develop into mature tissue-resident macrophages. Their
development is governed by two distinct sets of transcription factors. First, in the pre …