Age-dependent changes of the mesenteric lymph node of Fischer F344 rats: morphological and histometric analysis

Changes in mesenteric lymph nodes from Fischer F344 rats ranging from 5 to 37 months were studied by histological and histometric techniques. The most drastic histological changes were observed between 12 and 37 months of age. These changes include: loss of cellularity in the cortex; decrease in the number of germinal centers; distension of the medullary sinuses; decrease in the ratio of cortical area to medullary area; and infiltration of fibroblastic cells in the cortex and the medulla. Our results indicate a general structural disorganization in the mesenteric lymph node with increasing age. Such structural disturbance might be an important extrinsic factor for the decline in lymphocyte functions.