Virulent Treponema pallidum promotes adhesion of leukocytes to human vascular endothelial cells

Perivasculitis and endothelial cell abnormalities are characteristic histopathologic features of syphilis, a sexually transmitted disease caused by Treponema pallidum. To extend earlier studies demonstrating that T. pallidum activates endothelial cells, we now show that virulent T. pallidum, but not heat-killed T. pallidum or nonpathogenic Treponema phagedenis, promotes increased adherence of lymphocytes and monocytes to human umbilical vein endothelial cells. Lymphocytes and monocytes are the two cell types prominent in the histopathology of syphilis. Recognition that T. pallidum can stimulate endothelial cells to bind leukocytes provides important insights into the early mechanisms of syphilis immunopathogenesis.