Tridimensional study of the deep cortex of the rat lymph node. II: Relation of deep cortex units to afferent lymphatic vessels

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Abstract
Recently, we reported that the deep cortex of the rat lymph node is formed of semi‐rounded structures, the “deep cortex units,” contiguous to the peripheral cortex and bulging into the medulla. It was suggested that a unit represents an accumulation of lymphocytes centered on the opening of an afferent lymphatic vessel. To verify the proposal, we carried out a tridimensional analysis of serially sectioned rat nodes, fixed by perfusion and trimmed in such a way as to preserve their lymphatics. The tridimensional analysis revealed that a constant topographical relationship exists between the units and the openings of the afferent lymphatics. The results demonstrated that the topographical organization of the deep cortex of a rat node correlates with the distribution pattern of the opening(s) of its afferent lymphatic(s). The overall observations suggested the following explanation for the shape and topography of the units: factor(s) present in the lymph would spread in a radial manner from the opening(s) of an afferent lymphatic through the underlying cortex. The factor(s) would induce morphological modifications in the stimulated semi‐rounded area which, in turn, would provoke a local accumulation of circulating lymphocytes.