MECHANISMS OF IMMUNITY TO LEISHMANIASIS .1. EVIDENCE FOR A CHANGING BASIS OF PROTECTION IN SELF-LIMITING DISEASE

Abstract

Methods of adoptive immunization were employed to analyze the mechanisms of acquired immunity to leishmanial infection in the guinea pig. Resistance developed 2 wk after infection. Protection could be passively transferred to normal recipients with short-lived T [thymus-derived] lymphocytes. Although cells taken from animals at progressive stages of the disease could adoptively immunize normal recipients, their effectiveness waned from 8 wk onward. Concomitant serum transfer performed at progressive times during the infection failed to augment the level of immunity generated in normal recipients and at certain times appeared to have an inhibitory effect on this phenomenon. Serum from convalescent animals augmented the level of adoptive immunity expressed in recipients. Serum taken from recovered animals 24 h after re-challenge could transfer immunity to normal recipients. Using immunofluorescent techniques to assay titers of anti-leishmanial antibody [Ab], a temporal relationship was found between high Ab titers and the ability of serum to contribute positively to the adoptive immunization of normal recipients. The basis of the protective immune response to leishmanial infection may change during the course of the disease from a purely cell-mediated mechanism to one involving protective Ab.