<b>Three-dimensional reconstruction of serial sections for analysis of the microvasculature of the white pulp and the marginal zone in the human </b><b>spleen </b>

Abstract

Although a number of papers have given useful information on splenic microcirculation by light and/or scanning electron microscopy, controversies remain as to the vascular arrangement, especially in the human spleen. The present study re-examined the microvasculature of the human spleen using a three-dimensional reconstruction of immunohistochemically stained tissue sections, and showed that the central artery does not directly issue follicular arteries in the human spleen; follicular arteries are derived from penicillar arteries outside the follicle and end in the white pulp. We found that the splenic follicle is surrounded by an elaborate system of anastomosed capillaries in both the marginal zone and the superficial layer of the white pulp. Most of these capillaries are also branches of the penicillar arterioles that are issued from the central artery in the same, or a different, white pulp system. Because the endothelia of these capillaries are widely open in the marginal zone, this vascular network may play a major role in supplying blood to the marginal zone. The accumulation of sialoadhesin-positive macrophages was also observed around the vascular network, suggesting an important role for this structure as the front line of immune response.

Three Dimensional Reconstruction

“…2.10), but no CD34-positive capillary endothelial cells inside the follicles. This corresponds to the results of others [Kusumi et al, 2015]. The histological reason for this fact needs to be investigated in more detail.…”

“…We reconstructed the capillaries inside and outside the follicles. Before our efforts (Chapter 7), only one study existed on this topic [Kusumi et al, 2015]. Fig.…”

“…We suggest that specialised stromal marginal reticular cells form a barrier inside the splenic marginal zone, which together with the scarcity of capillaries guarantees the maintenance of gradients necessary for positioning of migratory B-and T-lymphocytes in the human splenic white pulp. T h e s p l e e n is the organ with the most enigmatic microvasculature, both in humans and in rats or mice [Snook, 1964, Balázs et al, 2001, Kusumi et al, 2015. In all three species the main part of the organ, the so-termed red pulp, harbours two types of microvessels, namely capillaries and sinuses, which form the end of the arterial tree and, respectively, the beginning of the venous part of the circulation.…”

Emerging Role of the Spleen in the Pharmacokinetics of Monoclonal Antibodies, Nanoparticles and Exosomes

“…Furthermore, another area of controversy concerning the blood supply of the white pulp has been recently addressed by 3D reconstruction studies. Kusumi et al [11] showed that different from what was suggested by previous evidence, the central arteries do not directly contribute to the vascularization of the white pulp. The white pulp is, instead, irrorated by harpin loop arterioles emerging from the penicillary artery; after that, it leaves the follicle or the lymphoid sheath surrounding the central artery.…”

Heterogeneity of Memory Marginal Zone B Cells

“…Because of their anatomical location at the border of the red pulp, they have a rich supply of capillaries that are widely open. 4 MZ-B cells are thought to play an important role in rapid immune responses against bloodborne pathogens. In particular, they are believed to respond rapidly to polysaccharide antigens (TI-2 antigens), which are present on the surface of encapsulated bacteria such as pneumococci and meningococci.…”