Changes in histology of the regional lymph nodes and in the proportions of T and B cell populations by oxazolone painting or LPS injection in guinea pigs.

Changes in the regional lymph nodes from guinea pigs stimulated with oxazolone painting or LPS injection were examined by light and electron microscopy at various intervals. The proportions of T and B cells in the nodes were estimated by rosette formation technique30,34 and weights of the thymus and spleen were measured at the same time. The first event occurring in the nodes after antigenic stimulation was increase in number and activity of post-capillary venules (PCV) which resulted in augmentation of an influx of small lymphocytes from the recirculating pool. Lymphocytes which streamed into the nodes promptly flowed out through the sinus endothelium into the pool. The second event was specific accumulation of committed lymphocytes35. The proportion of T cell in the node suspension reached a peak 4 days after oxazolone painting when morphological changes became maximum and the thymus enlarged. On the other hand, in LPS group, B cells reached a peak on day 5 or 6 when relatively immature germinal centers increased in the nodes and decreased on day 7 because of their differentiation into plasma cells.