Antigenic influence at critical terms of ontogenesis can cause significant changes in the child's immune system. It is known that the entry of antigens into the fetus causes premature release of T-lymphocytes from the thymus and their migration to various organs. The paper was aimed at the study of the folliclegenesis of the thyroid gland in postnatal period at norm and after prenatal influence of staphylococcal toxoid. In the experimental research as a material were thyroid glands of Wistar rats aged 1 to 60 days of postnatal development (162 animals), about 6 animals in each group. Three animals groups were studied on 1, 3, 7, 11, 14, 21, 30, 45, 60 days after bith. I gr. - intact animals (norm); ІІ gr. - control, animals which were injected intrauterine 0.9% NaCl solution; III - experimental animals injected with staphylococcal toxoid liquid purified adsorbed (10-14 units of binding in 1 ml, diluted 10 portions) by operation intrauterinely on the 18th day of dated pregnancy. Histological sections 3-5 μm thick were stained by hematoxylin and eosin, histochemicaly by alcian blue and azan staining. Immunohistochemical study was performed according to the protocol recommended for a particular antibody of the manufacturer. Used ki-67 (Ki-67), TTF-1 (8G7G3/1), Fox-1 (A-12) monoclonal antibodies by Santa Cruz Biotechnology, Inc. A set of morphometric studies was performed by microscope Carl Zeiss Primo Star equipped with the Axiocam digital microphoto attachment with using program complex Zeiss Zen 2011. The results were considered reliable at p≤0,05. For processing of statistical material was used the standard software package Microsoft Office Excel and Statistica 10.0.The results were obtained about morphogenesis of rat’s thyroid after intrauterine antigenic action of staphylococcal toxoid. Morphofunctional homeostasis and stromal-parenchymal proportional relationship to thyroid gland closely associated with the activity of immune cells, including special role of lymphocytes, macrophages, and mast cells. Prenatal influence of staphylococcal toxoid led to the formation of a more pronounced structure of the parenchyma and stroma, but they showed signs of functional immaturity after birth. During the sucking period, the simultaneous presence of intra-, extrafollicular, septal and intramural types of folliculogesis is determined, which is a local reaction to systemic antigenic irritation with activation of compensatory-adaptive reactive folliclegenesis. The revealed changes in the process of folliclegenesis, accompanied by venous plethora, the formation of intraorgan diffuse lymphoid tissue and nodules, desquamation of the follicular epithelium, redistribution of the follicle diameter is a reaction to the systemic antigenic effect on the body during the critical period of prenatal development and normalizes by 45 days.Keywords: morphogenesis, thyroid gland, antigen, staphylococcal toxoid, experiment.