POSTNATAL-DEVELOPMENT OF INTRAEPITHELIAL LEUKOCYTES IN THE CHICKEN DIGESTIVE-TRACT - PHENOTYPICAL CHARACTERIZATION IN-SITU

In the present study, we characterized intra-epithelial leukocytes in the digestive tract of chickens during postnatal development. Their ph enotype was characterized by monoclonal antibodies in cryostat section s and the numbers of the different cell-types were counted in the epit helium of the esophagus, proventriculus, duodenum, jejunum, cecum, and colon. All intra-epithelial leukocytes bore the leukocyte-common anti gen CD45; 35% were T lymphocytes, and 50% bore a B-cell marker. Howeve r, no immunoglobulin-bearing cells were detected in the epithelium. Mo nocytes and macrophages were found only in the epithelium of the esoph agus. A remaining population of non-B, non-T, non-monocyte cells (15%) was present in all parts of the digestive tract. The number of intra- epithelial leukocytes was greatest in the duodenum and jejunum, and de creased in the proximal part of the cecum and in the colon. Intra-epit helial leukocytes were only sporadically detected in the proventriculu s. The total number of intra-epithelial leukocytes increased until 8 w eeks after hatching and then decreased at 18 months. In the esophagus, the total number of intraepithelial leukocytes changed little during aging. We found that the intra-epithelial leukocytes of chickens and r odents are distinct in that chicken intra-epithelial leukocytes compri se a cell population that bears a B-cell antigen but that lacks surfac e immunoglobulins.