Lymphatic vessel hypertrophy in inflamed human tonsils.

The structural and molecular properties of the human tonsil lymphatic microvascular system are important to understand as these features likely contribute to fluid balance, immunity, and tumor metastasis. The tonsil is a unique lymphoid organ in that it is in intimate contact with the contents of the upper aerodigestive tract and that there are no identifiable afferent lymphatics. Conventional immunofluorescence microscopy demonstrated a remarkable degree of lymphatic vessel architecture within the tonsil; LYVE-1-positive lymphatic vessels were detected around each germinal center and in the marginal regions between the follicles. High resolution confocal laser scanning immunofluoresence microscopy demonstrated that individual lymphatic endothelial cells had a classic 'oak leaf' shape and discontinuous expression of CD31 and VE-cadherin; characteristics hypothesized to be related to fluid and cellular transport. A comparative analysis demonstrated a dramatic increase in lymphatic but not blood vessel density and complexity in inflamed compared to noninflamed tonsil tissue. The results of this study describe the spatial organization of the tonsil lymphatic vasculature, discontinuous expression of CD31 and VE-cadherin in human lymphatic capillaries, and a change in lymphatic vessel morphology in response to inflammation.