REGULATION OF B-CELL DIFFERENTIATION BY ANTIGENIC STIMULI ACROSS BURSAL EPITHELIUM IN NEONATAL CHICKEN

Abstract

The bursa of Fabricius is known as the major site for B-cell differentiation. It is well established that various antigenic materials derived from the gut or artificially introduced into the cloacal lumen are trapped into the bursal lumen by sucking movements. This chapter discusses a study to investigate the regulatory role(s) of specific and/or nonspecific stimuli across the bursal epithelium on B-cell differentiation in neonatal chicken by using two different systems. When neonatal chickens were intracloacally primed with sheep red blood cells (SRBC) and then intravenously challenged with the same antigen, markedly enhanced plaque forming cell (PFC) response in the spleen was observed. The bursal duct was ligated on the 19th day of incubation without any damage on the blood, and lymphatic vasculature, and subsequent development of the bursa, and of the immune reactivity was examined. The size of the bursal lymphoid follicles of these chickens was slightly smaller than those of controls. Neither necrotic changes nor severe involution of the bursal lymphoid follicles was observed at any age examined, and lymphopoiesis in the bursa gradually increased with age. It is found that when immune reactivity of these chickens was examined by anti-SRBC PFC response, marked suppression was observed, although the reactivity gradually increased with age. It is observed that when bursal duct ligation was performed one week after hatching, no or only very minor effect was observed in the development of the immune system.