Cell Proliferation, Apoptosis, and B- and T-Lymphocytes in Peyer's Patches of the Ileum, in Thymus and in Lymph nodes of Preterm Calves, and in Full-Term Calves at Birth and on Day 5 of Life

Abstract

Peyer's patches, thymus, and lymph nodes contain the majority of lymphocytes. We have studied proliferation rates, apoptosis rates, and numbers of B- and T-lymphocytes in Peyer's patches in ileum, thymus, and mesenterial and prescapular lymph nodes (LM and LP) in unfed preterm calves (GrP; born 13 d before expected normal term after dams were injected with prostaglandin F2α and glucocorticoids) and normal-term calves (GrF) immediately after birth and on d 5 of life after feeding colostrum for 4 d (GrC). Immunohistochemical methods in conjunction with incorporation of 5-bromo-2′-deoxyuridine or terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling were used to evaluate cell proliferation rates and apoptosis rates, respectively. The number of T- and B-lymphocytes was determined with monoclonal antibodies directed against CD3 and CD79, respectively. In GrF compared with GrP, there were higher numbers of proliferating and apoptotic cells in LM and LP, of B-lymphocytes in paracortex and follicles of LM and LP, and of proliferating cells in cortex and medulla of thymus. In thymus cortex and medulla, numbers of proliferating cells were higher in GrC than in GrF. Apoptotic rates were generally smaller at all sites of Peyer's patches in GrC than in GrF, and proliferation rates increased from GrP to GrF in intrafollicular areas and from GrF to GrC in all tissues. Numbers of T-lymphocytes in Peyer's patches were higher in GrF than in GrP, but lower in GrC than in GrF, except in the domes. Numbers of B-lymphocytes did not change in Peyer's patches despite high proliferation and low apoptotic rates, suggesting that they leave Peyer's patches during the first days of life. In conclusion, proliferation and apoptosis rates and numbers of B- and T- lymphocytes in Peyer's patches in ileum, thymus, and LM and LP exhibited different developmental changes and were affected by feeding.