In Vivo Effects of Cortisone on the B Cell Line in Chickens

The effects of a single dose of cortisone acetate (5 or 10 mg/100 g body weight) on B cells were examined in young chickens. A dose-dependent increase in numbers of circulating B lymphocytes and a change in their Ig-class distribution were followed by parallel increase in splenic plasma cells and serum immunoglobulins. The higher dose of cortisone produced changes in Bmu and Bgamma cells, whereas the lower dose primarily affected Bmu cells. These steroid-induced changes were preceded by lymphocyte depletion in the cortical regions of bursal follicles, and prior bursectomy prevented steroid-induced increases in circulating B lymphocytes and tissue plasma cells. The results suggest that cortisone can induce bursal lymphocytes to migrate from the bursa and to settle subsequently in peripheral lymphoid tissues where they become mature plasma cells.