Mazurkevych T. Morphofunctional features of immune formations of domestic duck intestine (Anas platyrhynchos var. domestica) in the postnatal period of ontogenesis

Immune formations of duck intestines are represented by Peyer's patches, which are absent in the rectum, Meckel's diverticulum and apical diverticula. Their morphometric parameters change almost synchronously with the change in the length of the intestines in which they are located. Their maximum morphometric parameters are registered in 120–150-day-old ducks. The wall of immune formations has the same tunics as the wall of the intestine. Lymphoid tissue, which determines the functions of immune formations, is located in their tunica mucosa and tunica muscularis. The maximum value of the area of this tissue in some formations is registered in ducks of different ages, and its full morphofunctional maturity occurs at 10-20 days of age of the fowl. Cells involved in the development of the immune response, structural cells of its membranes and blood cells were found in the wall of immune formations. Among them, most contain lymphocytes. Early and mature B-lymphocytes, naive T-cells, T-helpers, T-suppressors and natural killers were found in the lymphoid tissue of immune formations of ducks aged 30, 150 and 180 days, and blood stem cells were found in some areas of ducks aged 180 days.