Lack of proliferation of circulating white blood cells in patients with syphilis before and after a Jarisch-Herxheimer reaction.

The occurrence of lymphoblasts in peripheral blood, measured by incorporating tritiated thymidine ([3H]dThd), was studied before, during, and after a Jarisch-Herxheimer reaction in patients with early syphilis. No difference in [3H]dThd incorporation into peripheral white blood cells was found between five patients with syphilis and 19 healthy controls, whereas in 20 cord blood samples [3H]dThd incorporation was significantly increased.