The following stages in lymphoid patches (LP) development have been revealed: I-1-6, II-7-14, III-15-21, IV-22-30 days; during these periods lymphoid noduli with germinative centers, cupolae and internodular areas are formed. Amount of all kinds of cells in the LP parenchyma and their rearrangement in the zones takes place. In one-month-old rats blast forms predominate in the LP germinative centers, and small lymphocytes--in the zone of small lymphocytes of the noduli and internodular areas. Under conditions of antenatal effect of an antibiotic on the system mother--fetus there is no disturbances in formation of the anatomical structures. However at each stage of development the small intestine LP are not mature, concerning their cellular composition. Amount of cells decreases, their interrelationship changes. Lympho- and plasmocytopoiesis decreases.
