[Structure of the thymus, iliac and mesenteric lymph nodes in the rat at different stages of pregnancy].

Development of pregnancy results in a systemic reaction of the immunogenetic organs: the structure of both the central (thymus) and peripheral lymphoid organs (lymph nodes) undergoes certain changes, beginning from its earliest stages (preimplantation period). Unidirection of the processes in the iliac (that are regional for the uterus) and mesenteric lymph nodes is stated. The reconstruction of the node occurs according to the reaction type at tissue allotransplantation, when hypertrophy of the thymus-dependent zone comes forward. During the period of the greatest manifestations of these alterations, however (the second half of pregnancy) the migration process of lymphocytes from blood into the lymph node is significantly inhibited. This is essentially clear in the iliac lymph nodes. The reconstruction of the thymus is in general similar with phenomena of accidental involution. However, accumulation of thymocytes in the medulla demonstrates blocking of their discharge into the blood stream. The disturbed processes of recirculation of result in incompleteness of the immune response at pregnancy and, perhaps, are included into the protective mechanisms of the offspring reproduction.