This in turn will facilitate vaccine development. A good example is leishmania infection. The acute stage of this disease is resolved by DTH-macrophage activation. Leishmanial components preferentially activate Th2 lymphocytes. This selects for Th1 predominance and generates protective immunity.
Syphilis exhibits many parallels to the other nine chronic diseases mentioned above.
Some of the complexities of immunoregulation during treponemal infection have just begun to be unraveled. Macrophages seem to be intimately involved in the mechanics of this switch, and their specific role needs further clarification. Whatever is learned about syphilis, as well as other chronic infections will contribute to a better understanding of the generalized pathways of immunoregulation. Syphilis superinfection activates expression of human immunodeficiency virus I in latently infected rabbits.