Reactivity of Spleen Germinal Centres in Immunized and ACTH-treated Chickens

Graczyk S., J. Kuryszko, J. Madej: The Reactivity of Spleen Germinal Centres in Immunized and ACTH-treated Chickens. Acta Vet. Brno 2003, 72: 523-531. The aim of the study was to estimate the reactivity of spleen white pulp structures in chickens immunized with sheep erythrocytes (SRBC) and remaining under the influence of ACTH. The 11week-old chickens were divided into four groups. Group I constituted the control, while chickens of groups II and IV were immunized with SRBC. Chickens of groups III and IV were given ACTH. The sections of thymus, bursa of Fabricius and spleen were done and used for histological evaluation. The number of germinal centres of the types I and II was estimated on the determined spleen surface. It was shown that after SRBC administration in the thymus cortex and in medulla of bursa of Fabricius, proliferation of lymphoid cells was visible. However, after ACTH administration in the discussed thymus and bursa parts, lymphocyte depletion was observed. Morphometric analysis of the spleen showed that after the administration of SRBC and ACTH there is observed the increase in the number of the type II germinal centres. The results of the study indicated the diversified antigen influence on the morphological picture of the lymphatic organs. They also showed different sensitivity of particular structures to administered ACTH. Moreover, the earlier observations and current results allowed to work out the model of formation and movement of different types of germinal centres in the spleen. Chickens, spleen, germinal centres, ACTH, SRBC Numerous environmental factors evoke in an animal organism a set of functional and morphological changes, called stress by H. Selye. These changes most often lead to an adaptation, making it possible for the organism to survive in the changing conditions. According to Puvadolpirod and Thaxton (2000ab), in birds it is difficult to specify a typical stress picture and predict the course of stress. This results not only from the variety of stressors but most of all, from the character of the reaction, in which main coordination systems of the organism play a dominant part. An important role is played by the endocrine system and its hormones, especially glucocorticoids which, ensuring the development of adaptation, at the same time contribute to protection against excessive activation of endogenous processes which threaten with self-destruction (T omaszewska and Przekop 1997; M itchell and Kettlewell 1998; Goldstein and McEwen 2002). A prolonged activation of the hypothalamic-pituitary-adrenal axis is responsible, among others, for metabolic changes and changes in cells and tissues of the lymphatic system. It has been shown that both the stressors and parenteral administration of ACTH to birds leads, to clear changes in circulating blood, through activation of the above