Distribution of B-lymphocytes in the areas of bursal and cloacal lymphoid infiltration.

The present study was carried out on the Diffusely Infiltrated Area of the bursa of Fabricius (DIA) and the area of lymphoid infiltration of the dorsal wall of the cloaca, using immunoperoxidase and electron transmission microscopy, in order to verify the behaviour of antibody-producing cells and their distribution in the two organs. An anti-chicken Ig antiserum was used for this purpose, and the results obtained show that there is a progressive increase in the antibody-producing cells in the DIA, and subsequently also in the cloaca, during the first few weeks of life; the percentage values remain constantly higher in the DIA compared with the cloaca. Electron microscopy made it possible to detect numerous lymphocytes and some plasma cells in the epithelium. Many of the intra-epithelial lymphocytes were immunoperoxidase-positive. The possible role played by the B-lymphocytes found in both organs is discussed.