Histo- and cytological, histo- and cytochemical characteristics of immune system of small intestine wall of fetal and calves of newborn stage of development

The development of immune structure of small intestine wall occurs consistently in three stages. The first stage is a laying (from 30 – 34 days to 3 – 4.5-months age of the fetus). The second is formation (in fetuses from 3 – 4.5 to 6 – 6.5 months) which has 2 stages: the first is differentiation of mesenchymal cells into lymphoci (in embryos from 3 to 4.5 months) and the second is a formation of single lymphoid nodules (in fetuses from 4.5 to 6 – 6.5 months). The third stage is a specialization (in fetuses from 6 – 6.5 months up to 15 days old in calves). The beginning of specialization is the formation of lymphatic nodules, forming within it blood centers and differentiation of plasmacytoids from plazmoblasts.