Three-dimensional human germinal centers of different sizes in patients diagnosed with lymphadenitis show comparative constant relative volumes of B cells, T cells, follicular dendritic cells, and macrophages

Germinal centers (GCs) are some of the most important structures in the human immune system. As such, their cell types and functions have been thoroughly investigated. B cells, T cells, follicular dendritic cells (FDCs), and macrophages have widely been found to typically be aggregated in GCs. However, the amount of space occupied by each of these cell types has yet to be investigated. In this study, we conducted confocal laser-based 3D cell-volume quantification of typical GC cells under reactive conditions in lymphadenitis and investigated how volume proportions change during GC development. For this investigation, we used anti-CD3 (T cells), anti-CD20 and anti-Pax5 (B cells), anti-CD23 (FDCs), anti-CD68 (macrophages), and DAPI (nuclear staining). We detected average proportions of about 11% CD3, 9% CD20, 6% CD23, and 2% CD68 in the largest possible regions of interest within GCs. Interestingly, these values remained steady relatively independent of GC size. The remarkably low B cell proportion can be attributed to technical constraints given the use of the CD20 antibody in 3D. Applying the B cell marker Pax5, we found that about 44% of the volume was occupied by B cells after extrapolating the volume of B cell nuclei to that of whole B cells. We concluded that Pax5 is more suitable than anti-CD20 for 3D B cell quantification in GCs. The substantial unstained volume in GCs raises the question of whether other cell types fill these open spaces. Our 3D investigation enabled a unique morphological and volumetric evaluation of GC cells that balance their overall volumes in GCs.

3D connectomes of reactive and neoplastic CD30 positive lymphoid cells and surrounding cell types

Classical Hodgkin lymphoma (cHL) is one of the most common malignant lymphomas in Western Europe. It is diagnosed on the basis of histological sections by pathologists using a light microscope. The tumor cells, the Hodgkin- and Reed Sternberg cells (HRS), are visualized by morphology and positive response for the CD30-antigen. The same antigen can also be detected by immunohistochemistry on a reactive counterpart, showing CD30⁺ cells in special immunoreactions, such as inflammations of lymph nodes (lymphadenitis). CD30⁺ cells in reactive and neoplastic conditions are surrounded by lymphocytes and histiocytes, forming a micromilieu that enables the survival of the tumor cells, as well as their reactive counterparts. This study deals with an investigation of CD30⁺-surrounding cells using a confocal laser technology, visualizing the contacts of reactive and neoplastic CD30⁺ cells with CD68⁺ macrophages and CD163⁺ macrophages as well as to PD1⁺ lymphocytes and B cells (CD20⁺). CD4 immunostains were not included, because CD4⁺ cells were too numerous for clear dissection of single cells. 3D images visualized the, so-called, connectomes. Clear differences in the number of contacts between CD30-reactive and neoplastic cells (HRS) with macrophages and B lymphocytes were visible. Lymphadenitis and Mixed Cellularity type of classical Hodgkin Lymphoma (cHL) differed in that Mixed Cellularity (MC) cHL had more connections to macrophages (CD163⁺) and lower number of connections to B cells (CD20⁺). The connectomes of both Hodgkin variants MCcHL and Nodular Sclerosis cHL (NScHL) mainly differed in the number of contacts to CD163⁺ macrophages, which was higher in MCcHL. Investigating the volumes of CD30⁺ -reactive and neoplastic cells, we found out that reactive cells showed lesser volumes, which correlated with the number of contacts. The comparison between 2D and 3D images, including 3D prints, demonstrated clear advantages of the 3D method. 3D images visualized significantly more and clearly defined intercellular contacts. Complicated cellular networks and their contacts became especially evident in volume and surface evaluations, as well as in 3D prints.

Detection of follicular regions in actin-stained whole slide images of the human lymph node by shock filter

Human lymph nodes play a central part of immune defense against infection agents and tumor cells. Lymphoid follicles are compartments of the lymph node which are spherical, mainly filled with B cells. B cells are cellular components of the adaptive immune systems. In the course of a specific immune response, lymphoid follicles pass different morphological differentiation stages. The morphology and the spatial distribution of lymphoid follicles can be sometimes associated to a particular causative agent and development stage of a disease. We report our new approach for the automatic detection of follicular regions in histological whole slide images of tissue sections immuno-stained with actin. The method is divided in two phases: (1) shock filter-based detection of transition points and (2) segmentation of follicular regions. Follicular regions in 10 whole slide images were manually annotated by visual inspection, and sample surveys were conducted by an expert pathologist. The results of our method were validated by comparing with the manual annotation. On average, we could achieve a Zijbendos similarity index of 0.71, with a standard deviation of 0.07.

3D investigation shows walls and wall-like structures around human germinal centres, probably regulating T- and B-cell entry and exit

This study deals with 3D laser investigation on the border between the human lymph node T-zone and germinal centre. Only a few T-cells specific for antigen selected B-cells are allowed to enter germinal centres. This selection process is guided by sinus structures, chemokine gradients and inherent motility of the lymphoid cells. We measured gaps and wall-like structures manually, using IMARIS, a 3D image software for analysis and interpretation of microscopy datasets. In this paper, we describe alpha-actin positive and semipermeable walls and wall-like structures that may hinder T-cells and other cell types from entering germinal centres. Some clearly defined holes or gaps probably regulate lymphoid traffic between T- and B-cell areas. In lymphadenitis, the morphology of this border structure is clearly defined. However, in case of malignant lymphoma, the wall-like structure is disrupted. This has been demonstrated exemplarily in case of angioimmunoblastic T-cell lymphoma. We revealed significant differences of lengths of the wall-like structures in angioimmunoblastic T-cell lymphoma in comparison with wall-like structures in reactive tissue slices. The alterations of morphological structures lead to abnormal and less controlled T- and B-cell distributions probably preventing the immune defence against tumour cells and infectious agents by dysregulating immune homeostasis.