Amplification of plaque-forming cells in the spleen after intracloacal antigen stimulation in neonatal chicken.

Neonatal chickens were primed by multiple or a single injection with sheep red blood cells (SRBC) into the cloacal lumen and then were challenged by intravenous injection with the same antigen. Direct plaque-forming cells (PFC) in the spleen were markedly increased shortly after intracloacal priming. This enhancing effect was antigen specific and was abolished by surgical bursectomy 24 h after intracloacal priming. A similar effect was also found in mature adult chickens, although the degree of enhancement was far less than that found in neonatal chickens. These results suggest that a certain stage of B-cell differentiation in the bursa of Fabricius (BF) is regulated by antigenic stimulation.