Distribution and spatiotemporal development of organised lymphoid tissues in the chicken intestinal tract.

Chickens exhibit a distinct immune architecture characterised by the absence of draining lymph nodes and the presence of a well-developed mucosa-associated lymphoid tissue. The structure and spatiotemporal development of chicken lymphoid tissues in the intestine are poorly documented. The macroscopically indistinct structure of chicken Peyer's patches has impeded studies into their development. The generation of CSF1R-eGFP reporter transgenic chickens enables visualisation of the development, organisation and extent of chicken lymphoid tissues by unique macroscopic views. CSF1R-eGFP reporter transgenic chickens were used to investigate the distribution and spatiotemporal development of PP and caecal tonsils in embryonic day 18 to 8-week-old chickens. Peyer's patch anlagen are present at ED18 with a similar frequency and distribution pattern observed in 2- and 8-week-old chickens. These findings can support in ovo and post-hatch mucosal vaccination strategies and the development of vaccine delivery systems targeted to the specialized epithelium overlying the Peyer's patches.