All antibodies used cross-reacted with shrew leukocytes. The B cell markers CD45R and CD79a were expressed by B cells, CD45R being strongly expressed in follicular germinal centres, but relatively faintly in well-differentiated B cells within follicular mantle zones, whereas CD79a was mainly expressed by mature B cells (weak expression in germinal centres (dark zone), strong expression in the periphery of secondary follicles, positive reaction of all cells in primary follicles). Plasma cells were negative or exhibited faint staining for both B cell markers. CD3 acted as a pan T cell marker, being expressed by entire T cell zones. Both the myeloid/histiocyte antigen and lysozyme were markers for mature monocytes/macrophages and their precursors, myelomonocytic cells, as they were expressed by monocytes and macrophages and a high percentage of cells in the bone marrow. However, they seemed not to be a marker for all neutrophils, as in both the splenic red pulp and sinuses of the pancreas of Aselli, a proportion of cells with the morphology of neutrophils were negative for both antigens. PCNA-positive, proliferating cells were present in follicle germinal centres, T cell zones, bone marrow (including megakaryocytes) and splenic red pulp, the sites in the haemolymphatic tissue expected to contain proliferating cells. The TUNEL method identified cells with the morphology of apoptotic cells [39, 41] as well as apoptotic bodies (both free and within tingible body macrophages), located predominantly in follicular germinal centres.