The effects of bacterial lipopolysaccharide (LPS) on high endothelial venules and interdigitating cells in mouse...

Migration of lymphocytes into lymph nodes is directly controlled by interaction of lymphocytes with the high endothelial venules (HEV), located in T cell-dependent areas of lymph nodes. Little is known about the mechanisms that regulate the activity of the HEV and the specificity of interaction with lymphocytes in various lymphoid organs. It has been suggested that the non-lymphoid interdigitating cells (IDC) play a role in maintaining the integrity of T cell areas. We therefore wished to determine whether the function of the HEV could be influenced by disturbing the integrity of the T cell area. This was assayed in mice by injecting bacterial lipopolysaccharide (LPS) in the hind footpad. The T cell-dependent areas of mouse popliteal lymph node were studied using immunohistochemistry, and attention was paid to the HEV specificity using short-term in vivo localization assays and in vitro lymphocyte binding assays. After LPS administration, apparent changes in the number of interdigitating cells and T cells in the draining lymph node were found. In addition, interdigitating cells lost their typical dendritic appearance. However, after LPS treatment, neither size, localization nor receptor specificity for lymphocyte subsets of HEV differed from control HEV. Although administered subcutaneously in the footpad, the effect of LPS on T cells and IDC was much more dramatic in the spleen than in the draining lymph nodes. This points to a difference in the processing of the endotoxin in the two organs.