Role of Harderian gland on differentiation and proliferation of immunoglobulin A-bearing lymphocytes in chickens.

The mechanism of accumulation of surface immunoglobulin A (sIgA) bearing cells in chicken Harderian gland (HG) was examined. Almost no sIgA-bearing cells were identified in HG of 1.5-week-old chickens. In 3.5-week-old chickens, however, 46.4% of the HG lymphocytes were sIgA-bearing cells. When bursa of Fabricius (BF) lymphocytes were transferred into recipients, BF lymphocytes migrated into the HG but the number of these lymphocytes was extremely small. In addition, no correlation was found between the surface immunoglobulin class of BF lymphocytes that migrated into HG and the migration. HG lymphocytes were co-cultured with HG whole cells (which contained 50-60% configurationally epithelial cells) in a non-contacting manner for 80 h using an Intercell culture vessel. The results showed a significant increase in the ratio of sIgA-bearing cells in HG lymphocytes compared with the control which was cultured without placing HG whole cells in the external well. B lymphocytes that migrated into HG seemed to undergo specific differentiation in situ into sIgA-bearing cells owing to microenvironmental factors, probably humoral factors excreted from HG epithelial cells, and subsequently undergo proliferation to result in accumulation of sIgA-bearing cells in HG tissue.