With growing molecular evidence for correlations between spatial arrangement of blood vasculature and fundamental immunological functions, carried out in distinct compartments of the subdivided lymph node, there is an urgent need for three-dimensional models that can link these aspects. We reconstructed such models at a 1.84 µm resolution by the means of X-ray phase-contrast imaging with a 2D Talbot array in a short time without any staining. In addition reconstructions are verified in immunohistochemistry staining as well as in ultrastructural analyses. While conventional illustrations of mammalian lymph nodes depict the hilus as a definite point of blood and lymphatic vessel entry and exit, our method revealed that multiple branches enter and emerge from an area that extends up to one third of the organ’s surface. This could be a prerequisite for the drastic and location-dependent remodeling of vascularization, which is necessary for lymph node expansion during inflammation. Contrary to corrosion cast studies we identified B-cell follicles exhibiting a two times denser capillary network than the deep cortical units of the T-cell zone. In addition to our observation of high endothelial venules spatially surrounding the follicles, this suggests a direct connection between morphology and B-cell homing. Our findings will deepen the understanding of functional lymph node composition and lymphocyte migration on a fundamental basis.

Previously, we designed a new quantitative phase-contrast setup for the microtomography experiments at the hereon beamlines P05 and P07 at PETRA III, DESY. This setup is based on Talbot array illuminators (TAI) as high visibility wavefront markers and can reach a spatial resolution level comparable to propagation-based imaging. In this work, we focus on the progress of bringing this setup into user operation. We collaborated with INI-Research to investigate the vascular system of mouse lymph nodes, exploiting the spatial resolution capabilities and using the quantitative aspect of the data to compare different sample preparation methods. We could successfully visualize and trace the blood supply of the lymph nodes, even with fine capillaries, showing the stability and performance of the setup in user application.