Cyto- and histological analysis of the whole immunogenic system at the development of an acute experimental appendicitis in rabbits has demonstrated that all the constituent parts of the system are involved into the reaction. In the central organ of immunity--thymus the main change is its progressive exhaustion, while peripheral organs of immunity are subjected to rather essential cytological rearrangements and activation of both cellular and humoral immunity. Accordingly to the type of the reaction, two groups of peripheral organs of immunity can be distinguish: the first--the appendix and the iliocecal lymph node which predominantly participate in the immunoblastic reaction and in the reaction of young plasmatic cells and demonstrate increased signs of immature cells emigration; the second--the axillary lymph node, as a representative of somatic nodes, and the spleen--the main carriers of the reaction in mature plasmic cells. Structural peculiarities of the complex appendix--iliocecal lymph node in intact animals and in the experiment make it possible to consider the complex as a peculiar functional link of the immune peripheral organs.