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First published online March 28, 2008
Journal of Experimental Biology 211, 1344-1351 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.012013

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CD14 and TLR4 are expressed early in tammar (Macropus eugenii) neonate development

Kerry A. Daly^1,2, Christophe Lefévre^2,3, Kevin Nicholas^2,3, Elizabeth Deane⁴ and Peter Williamson^1,2,*

¹ Centre for Advanced Technologies in Animal Genetics and Reproduction, Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia
² Cooperative Research Centre for Innovative Dairy Products, Australia
³ Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia
⁴ School of Environmental and Life Sciences, Macquarie University, Ryde, NSW 2109, Australia

^* Author for correspondence (e-mail: peter_williamson{at}usyd.edu.au)

Accepted 16 January 2008

Marsupials are born in a relatively underdeveloped state and develop during a period of intensive maturation in the postnatal period. During this period, the young marsupial lacks a competent immune system, but manages to survive despite the potential of exposure to environmental pathogens. Passive immune transfer via the milk is one well-recognised strategy to compensate the neonate, but there also may be innate immune mechanisms in place. In this study, CD14 and Toll-like receptor 4 (TLR4), integral molecular components of pathogen recognition, were identified and characterised for the first time in a marsupial, the tammar wallaby (Macropus eugenii). Functional motifs of tammar CD14 and the toll/interleukin receptor (TIR) domain of TLR4 were highly conserved. The lipopolysaccharide (LPS) binding residues and the TLR4 interaction site of CD14 were conserved in all marsupials. The TIR signalling domain had 84% identity within marsupials and 77% with eutherians. Stimulation of adult tammar leukocytes resulted in the induction of a biphasic pattern of CD14 and TLR4 expression, and coincided with increased production of the pro-inflammatory cytokine TNF-. Differential patterns of expression of CD14 and TLR4 were observed in tammar pouch young early in development, suggesting that early maturation of the innate immune system in these animals may have developed as an immune survival strategy to protect the marsupial neonate from exposure to microbial pathogens.

Key words: marsupial, innate immunity, microbial recognition, toll-like receptors, neonate