Mechanisms of immunity to leishmaniasis III. The development and decay of resistance during metastatic disease.

The development and decay of systemic resistance has been examined in guinea-pigs with progressive metastatic leishmaniasis. Adoptive cell transfer experiments have revealed that a T cell-mediated immune response develops 2 weeks after infection and confers a strong resistance to challenge on these animals which is expressed up to 5 weeks after initiation of infection. Beyond this time a decay of this resistance occurred. Loss of the ability to resist a challenge infection was not associated with a reduction in serum antibody levels which remained high in animals expressing no systemic resistance. Furthermore, cellular resistance could not be re-established in these animals by the infusion of immune lymphocytes from resistant donors. An examination of macrophage microbicidal capacity within metastatic and primary lesions revealed that progressive disease is associated with local suppression of macrophage effector function.