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Updated: Jun 10, 2026
A Murine Model of Fetal Exposure to Maternal Inflammation to Study the Effects of Acute Chorioamnionitis on Newborn Intestinal Development
Published on: June 24, 2020
Immaturity of the inflammatory response of the chick chorioallantoic membrane
J V Friend1, R W Crevel, T C Williams
1Unilever Research & Engineering, Environmental Safety Laboratory, Colworth House, Sharnbrook, Bedford MK44 1LQ, UK.
Abstract:
Previous tests on the chick embryo chorioallantoic membrane (CAM) had shown the 24- to 48-hr response to irritants to be necrosis, with a primitive granulation proliferation at the periphery. There were few heterophils (avian neutrophils). The present investigation confirmed the immaturity of blood leucocyte development. Few heterophils were seen at 14 days but were found in significant numbers on the 19th and 20th days just before hatching. The numbers of blood heterophils in 14-day-old embryos were almost doubled and the number of immature granulocytes slightly reduced when the CAM was treated with zymosan or N-formylmethionyl peptide, which are chemo-attractants for mammalian neutrophils. Treatment with chemicals that do not have selective activity for neutrophils, for example a surfactant or alcohol, did not stimulate this change. It was not feasible to pretreat 14-day-old embryos to increase the number of heterophils or to use 19- to 21-day-old embryos as a model to detect irritants inducing an acute inflammatory response, or to make the CAM more relevant as a substitute for the in vivo eye irritation test. No difference was found in the phagocytic ability of macrophages of 14-day-old embryos and 16-wk-old adults. Macrophages from both sources contained lactate dehydrogenase and beta-glucuronidase revealed by histochemical and fluorometric examination, and non-specific esterase by histochemistry, though staining was stronger in cells from the adults.
Insights
Chick embryo chorioallantoic membrane (CAM) tests show immature immune cells. Specific immune stimulants, but not general irritants, increase heterophils (avian neutrophils) in 14-day embryos, indicating limited use for in vivo eye irritation testing.
Area of Science:
- Developmental immunology
- Avian biology
- Inflammation research
Background:
- Chick embryo chorioallantoic membrane (CAM) models previously showed necrosis and limited heterophil response to irritants.
- Leukocyte development in chick embryos is immature, with few heterophils (avian neutrophils) early in development.
Purpose of the Study:
- To investigate the inflammatory response in chick embryo CAM, focusing on heterophil recruitment.
- To evaluate the effect of specific chemoattractants versus general irritants on embryonic immune cells.
- To assess the suitability of the CAM model for in vivo eye irritation testing.
Main Methods:
- Treatment of 14-day chick embryo CAM with zymosan and N-formylmethionyl peptide (chemoattractants).
- Treatment with non-selective chemicals like surfactants and alcohol.
- Histochemical and fluorometric examination of macrophage enzyme activity.
- Comparison of macrophage phagocytic ability between embryos and adult birds.
Main Results:
- Specific chemoattractants (zymosan, N-formylmethionyl peptide) significantly increased blood heterophil numbers in 14-day embryos.
- Non-selective irritants did not induce a similar increase in heterophils.
- Macrophage phagocytic capacity was similar between embryonic and adult cells.
- Macrophages from both embryonic and adult sources contained key enzymes like lactate dehydrogenase and beta-glucuronidase.
Conclusions:
- The chick embryo CAM model is limited for detecting general irritants or substituting in vivo eye irritation tests due to immature and specific immune responses.
- Immune cell recruitment in the CAM is dependent on specific chemoattractant signals, not general irritation.
- Embryonic macrophages exhibit functional and enzymatic similarities to adult macrophages.
