Capillary networks and follicular marginal zones in human spleens. Three-dimensional models based on immunostained serial sections

Abstract

We have reconstructed small parts of capillary networks in the human splenic white pulp using serial sections immunostained for CD34 alone or for CD34 and CD271. The three-dimensional (3D) models show three types of interconnected networks: a network with very few long capillaries inside the white pulp originating from central arteries, a denser network surrounding follicles plus periarterial T-cell regions and a network in the red pulp. Capillaries of the perifollicular network and the red pulp network have open ends. Perifollicular capillaries form an arrangement similar to a basketball net located in the outer marginal zone. The marginal zone is defined by MAdCAM-1+ marginal reticular stromal cells. Perifollicular capillaries are connected to red pulp capillaries surrounded by CD271+ stromal capillary sheath cells. The scarcity of capillaries inside the splenic white pulp is astonishing, as non-polarised germinal centres with proliferating B-cells occur in adult human spleens. We suggest that specialized 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.

Locating human splenic capillary sheaths in virtual reality

“…A paraffin-embedded sample of a normal human spleen which had been studied previously 23 and which was found representative of the majority of adult human spleens with small symmetric secondary follicles was processed to 24 serial sections which were simultaneously stained for CD34 and SMA in brown colour and for CD271 in blue (Fig. 1a,c,e ).…”

Expression of mucosal addressin cell adhesion molecule-1 on the reticular framework between white pulp and the marginal zone in the human spleen

“…28 It was also suggested that the specialized stromal marginal reticular cells form a barrier inside the MZ, which guarantees the maintenance of gradients necessary for positioning of migratory B and T cells in the WP. 30 In addition to cell adhesion molecules, the α-SMApositive reticular framework expresses the chemokines CCL21, CXCL12 and CXCL13 in the human spleen. 28,31 In the ontogeny of the human fetal spleen, α-SMA-positive stromal cells were demonstrated to express CCL21 and CXCL13, and induce the colonization of B and T lymphocytes into the WP.…”

The tempest in a cubic millimeter: Image-based refinements necessitate the reconstruction of 3D microvasculature from a large series of damaged alternately-stained histological sections

“…a. Healing in general We routinely use our opticalflow-based interpolation [67] to reduce the anisotropy of the data in our reconstructions [99,101]. Having initially acquired the data with spatial resolution of 0.5 µm/voxel × 0.5 µm/voxel × 7 µm/voxel, we produce volumes with 0.5 µm/voxel × 0.5 µm/voxel × 1 µm/voxel for the actual 3D reconstruction.…”

“…In practice, the final meshes were visualized in our virtual-reality-based application [66]. With the ability to place annotations and perform mesh painting, our software is used by the domain experts for knowledge discovery [99][100][101]. Fig.…”

“…The interaction of the experts with the model, the so-called visual analytics, is the actual way of finding insights and producing results. We developed a virtual realty application for this sake [66,99,101]. This paper, however, focuses on the cases when not everything works well in the required biomedical processing and the above 3D reconstruction pipeline.…”