Atrophy of lymph node compartments lacking lymph-carried lymphocytes in athymic rats

This paper reports on a form of atrophy of lymph node compartments occurring in mesenteric nodes of athymic nude rats whose perinodal tissue had become unusually rich in mast cells and fibrotic. The subcapsular sinus of an affected compartment was depleted of lymphocytes, while the medullary sinuses were loaded with macrophages. A progressive expansion of medullary sinuses into the medullary cords, the extrafollicular zone, the deep cortex unit and, finally, the folliculo-nodules of the compartment was accompanied by a gradual atrophy of the usual lymphoid cell populations of these nodal components. The occurrence of such a mode of atrophy of a compartment, associated with a lack of lymphocytes in the afferent lymph, agrees with our previous proposal that lymphocytes of the afferent lymph provide the stimuli for the development and maintenance of the structures of the node. The involvement of mast cells and fibrosis in the emergence of the present form of nodal atrophy, which further weakens the immune system of an immunodeficient animal, is considered.