Composition and Function of Haemolymphatic Tissues in the European Common Shrew

Bray, Daniel P.; Bennett, Malcolm; Stockley, Paula; Hurst, Jane L.; Kipar, Anja

The spleen in adult shrews exhibits lesser activity in the white pulp but higher cellularity in the red pulp compared to the spleen in sub-adults Red and white pulp of shrews of all age groups were examined for their composition and cellular turnover. The white pulp (lymphatic follicles and T cell zones) was generally confined to the organ's centre, where follicles were arranged singly or in groups ( Fig. 1 ). Germinal centres exhibited numerous proliferating, PCNA-positive cells (up to 50%) and few (#5%) apoptotic cells. T cell zones were arranged around medium-sized arteries, forming periarterial lymphatic sheaths similar in size and cell density in all animals, exhibiting up to 10% proliferating, PCNA-positive cells and generally few apoptotic cells. The generally cell-rich red pulp contained neutrophils, erythrocytes and smaller numbers of lymphocytes (each ,5% up to 30% T cells and mature B cells) and macrophages as well as numerous evenly distributed megakaryocytes (Fig. 1B) ; the red pulp exhibited some degree of cellular turnover, with approximately 10% proliferating, PCNApositive cells and scattered apoptotic cells. Follicles and follicle groups were often delineated by a variably distinct rim of macrophages and neutrophils (Fig. 1C) , together with variable numbers of mature, strongly CD79a-positive B cells, T cells and erythrocytes. In general, 30-50% of cells in the red pulp were positive for myeloid/histiocyte antigen (Fig. 1D ) and lysozyme and had the morphology of monocytes/macrophages or neutrophils.