Functional zones of Peyer’s patch (PPs) in rabbits’ caecum

A feature of rabbit gut-associated lymphoid tissue is that its structure is more developed than in other animal species. In rabbits it is composed of sacculus rotundus, vermiform appendix and Peyer’s patches. These immune formations contain an organized component of lymphoid tissue – lymphoid nodules (B-cell zone) and interfollicular region (T-cell). Secondary lymphoid nodules with germinal centers presented in them are formed due to antigen stimulation. The caecum of Hyplus rabbits at the age of 30 -, 60 - and 90-days was investigated. Each age group consisted of 5 rabbits. Experimental rabbits are clinically healthy, unvaccinated and untreated against ecto- and endoparasites. Peyer’s patches of the caecum were selected for the study and fixed in 10% of formalin. Subsequently, the specimens stained with hematoxylin-eosin were prepared from the obtained samples. On the 30th day of life, Peyer’s patches in the cecum were detected by gross examination. On the histological level, they had formed interfollicular region and lymphoid nodules. In turn, lymphoid nodules were divided into primary and secondary ones. A well-defined mantle zone and germinal centers were observed in the secondary lymphoid nodules. The regularities of their area indicators increase (mean value, median and interquartile range (IQR)) and their correlation were studied. The most intensive growth of the mantle area and the germinal center was observed from the 30th to the 60th day. The relative area of the mantle zone and the germinal center as part of the secondary lymphoid nodule was determined. Its value did not change during the experimental period.