Visualisation of chicken macrophages using transgenic reporter genes: insights into the development of the avian macrophage lineage

Abstract

We have generated the first transgenic chickens in which reporter genes are expressed in a specific immune cell lineage, based upon control elements of the colony stimulating factor 1 receptor (CSF1R) locus. The Fms intronic regulatory element (FIRE) within CSF1R is shown to be highly conserved in amniotes and absolutely required for myeloid-restricted expression of fluorescent reporter genes. As in mammals, CSF1R-reporter genes were specifically expressed at high levels in cells of the macrophage lineage and at a much lower level in granulocytes. The cell lineage specificity of reporter gene expression was confirmed by demonstration of coincident expression with the endogenous CSF1R protein. In transgenic birds, expression of the reporter gene provided a defined marker for macrophage-lineage cells, identifying the earliest stages in the yolk sac, throughout embryonic development and in all adult tissues. The reporter genes permit detailed and dynamic visualisation of embryonic chicken macrophages. Chicken embryonic macrophages are not recruited to incisional wounds, but are able to recognise and phagocytose microbial antigens.

Dynamics of Structural Barriers and Innate Immune Components during Incubation of the Avian Egg: Critical Interplay between Autonomous Embryonic Development and Maternal Anticipation

“…Immune cells such as macrophages enter the liver and kidneys at ED12 and ED16, respectively [116]. Already at ED4/ED5, embryonic macrophages are observed in the blood vessels and at perivascular locations; chicken embryonic macrophages are not recruited to incisional wounds, but they are able to recognize and phagocytose microbial antigens [117]. These immune cells can also be found in extra-embryonic membranes, particularly in the chorionic surface of the CAM in response to an immune challenge [118].…”

“…These immune cells can also be found in extra-embryonic membranes, particularly in the chorionic surface of the CAM in response to an immune challenge [118]. Moreover, macrophages are active in embryonic tissues; they can recognize and engulf microbes associated with blood vessel walls and respond to chemotactic signaling [117]. …”

“…Further analysis by proteomics and transcriptomics would provide a better understanding of the development of CAM defense mechanisms that protect the egg from pathogens. Moreover, live imaging of the CAM to gain insight into leukocyte recruitment, penetration, and response to pathogens, using, for example, colony-stimulating factor 1 receptor (CSF1R) reporter chicken immune cells [117], would be an exciting research avenue to explore.…”

Transgenic quail to dynamically image amniote embryogenesis

“…Although resolving the exact molecular mechanism that underlies this observation will require additional studies, the heterogeneity of chFP expression in Tg(PGK1:H2B-chFP) quail should help us better understand how cell proliferation rates contribute to the differential growth of various tissues and regions during early embryogenesis (Ridenour et al, 2012;SakaueSawano et al, 2008). The Tg(PGK1:H2B-chFP) quail adds to an ever-growing list of transgenic lines generated over the past decade in quail (Sato and Lansford, 2013;Sato et al, 2010;Scott and Lois, 2005;Seidl et al, 2013), chicken (Balic et al, 2014;Chapman et al, 2005;McGrew et al, 2004;Motono et al, 2010;Rozbicki et al, 2015) and songbird (Agate et al, 2009) that express reporter proteins in a ubiquitous or tissue-specific manner.…”

Distribution patterns of mucosally applied particles and characterization of the antigen presenting cells

“…This process is crucial for the induction of adaptive immune responses and for the maintenance of homeostasis (reviewed by Holt et al, 2008, Braciale et al, 2012. Although chickens lack draining lymph nodes, a highly developed mucosal immune system is present (Balic et al, 2014), with several organized mucosa-associated lymphoid tissues described in the intestinal tract, the respiratory tract and the eye region. The bronchus-associated lymphoid tissue (BALT), nasal-associated lymphoid tissue (NALT), Harderian gland (HG) and conjunctiva-associated lymphoid tissue (CALT) are thought to play important roles in induction of respiratory tract immune responses.…”