Structure, lymphatic vascularization and lymphocyte migration in mucosa‐associated lymphoid tissue

Abstract

In this review, we consider the morphological aspects and topographical arrangement of gut-associated lymphoid tissue (GALT) (solitary and aggregate lymph nodules or Peyer's patches) and of vermiform appendix in the human child and in some mammals. The spatial arrangement of the vessels belonging to apparatus lymphaticus periphericus absorbens (ALPA) and of blood vessels within each lymphoid follicle as well as the ultrastructural characteristics of the lymphatic endothelium with high absorption capacity are considered. Particular attention is also paid to the morphological and biomolecular mechanisms inducing lymphocyte transendothelial migration to the bloodstream by means of lymphatic vessels as well as their passage from blood into lymphoid tissue through the high endothelial venules (HEVs). The preferential transendothelial passage of lymphocytes and polymorphonuclear neutrophils within ALPA vessels of the interfollicular area does not occur following the opening of intercellular contacts, but rather it occurs by means of 'intraendothelial channels'. In HEVs, on the contrary, the hypothesis is plausible that lymphocyte transendothelial migration into lymphoid tissue occurs through a channel-shaped endothelial invagination entirely independent of interendothelial contacts. The lymph of ALPA vessels of the single Peyer's patch is conveyed into precollector lymphatic vessels and into prelymph nodal collectors, totally independent of the ALPA vessels of the gut segments devoid of lymphoid tissue. The quantitative distribution of T lymphocytes in the lymph of mucosal ALPA vessels suggests a prevalent function of fluid uptake, whereas a reservoir and supply function is implicated for the vessels of interfollicular area. The precollector lymphatic vessels and prelymph nodal collectors are considered to be vessels with low absorption capacity, whose main function is lymph conduction and flow.

Interstitial Fluid and Lymph Formation and Transport: Physiological Regulation and Roles in Inflammation and Cancer

“…Such structures have also been described in liver (335), lymphoid tissue (29), and lung (418). In the brain, nonendothelialized spaces between the internal vascular and the external glial basal laminae act as a prelymphatic drainage system (283).…”

Nasal Administration of Recombinant Rat α3(IV)NC1 Prevents the Development of Experimental Autoimmune Glomerulonephritis in the WKY Rat

“…Nasal administration means that the antigen is placed in direct contact with the inductive site on the nasal associated lymphoid tissue and is not altered by gastric proteases before presentation within gut associated lymphoid tissue (GALT). As a result, much lower doses of antigen are required to induce a tolerant state via the nasal route, then via oral administration (53,54).…”

Modeling emergent tissue organization involving high-speed migrating cells in a flow equilibrium

“…In a simplified model cells enter and leave the tissue through separate spherical areas that do not further interact with the system. However, one should be aware that in real SLT the lymphatic endothelium which may be involved in the efflux of cells is located exclusively outside the PLF [50][51][52][53][54][55][56][57][58][59][60]. Thus, there may be some interaction that couples PLF formation with the location of exit spots which we ignore in the presented toy model.…”