Effect of early fetal splenectomy on prenatal B-cell development in sheep

The contribution of early splenic B-cell populations to the colonization of the ileal Peyer's patch was investigated following the surgical removal of the spleen in a series of jh-day-old fetal sheep. The fetuses were killed at 140 days of gestation and the ileal Peyers patch, the distal jejunal lym ph node which drains the Peyer's patch, and a peripheral lymph node. the su perficial cervical lymph node, were examined. Enzyme and immunohistochemica l evaluation concluded that the distribution of B cells, T cells and stroma l cells in the ileal Peyer's patch was similar in splenectomized and normal feral sheep. Thus, the presence of the Trial spleen was not essential for the colonization of the ileal Peyers patch and other early sites of B-cell accumulation would appear capable of generating the necessary precursor pop ulations. Investigation of B-cell populations in lymph nodes used a combina tion of terminal deoxynucleotidyl-transferase-mediated deoxyuridine-triphos phate nick-end-labelling (TUNEL) histochemistry and immunofluorescence to d etermine the average number of apoptotic B cells in the primary follicles o f the outer cortex of splenectomized and normal lambs. A significantly incr eased number of apoptotic B cells was present in the distal jejunal lymph n ode but not in the superficial cervical lymph node of splenectomized lambs. This finding suggests that splenectomy affected prenatal B-cell developmen t in Fetal sheep and raises questions as to the regulation of B-cell lympho poiesis in a species using a post-rearrangement organ of diversification.