We study the progressive emergence and functional traits of the innate immune system in vertebrate development, taking advantage of the optical transparency of the zebrafish embryo and larva to address questions that are difficult to approach in mammals. Thus we have explored the successive developmental waves of hematopoiesis, from the emergence of hematopoietic stem/progenitor cells (HSPCs) to the deployment of resident leukocytes in the tissues. Then among these leukocytes, we investigate the respective behaviour and roles of the professional phagocytes, macrophages and neutrophils, in the developing organism.
In the above video of a transparent zebrafish embryo (at 28 hrs post fertilization) imaged non invasively by video-enhanced Nomarski microscopy, a global view of the embryo’s head and part of its yolk sac is followed by a close-up on the skin, then a progressively deeper focus shows the blood cells underneath – circulating pro-erythrocytes (round cells) and macrophages (cells with irregular contour), produced from the initial, so-called ‘primitive’ wave of hematopoiesis..
