HUMORAL IMMUNITY IN EXPERIMENTAL SYPHILIS .1. DEMONSTRATION OF RESISTANCE CONFERRED BY PASSIVE-IMMUNIZATION

Abstract

Evidence of a role for humoral factor(s) in immunity to experimental syphilis was provided by the demonstration that passive immunization of rabbits by daily i.v. injections of immune serum significantly delays the appearance and markedly diminishes the severity and duration of lesions which develop after challenge with Treponema pallidum. Five rabbits were injected daily over 37 days with 3 m/kg body weight of pooled immune rabbit serum injections with 1.1 .times. 103 T. pallidum, Nichols strain, at each of 4 sites. The animals developed atypical lesions of short duration after an average delay in onset of 28 days beyond the development of typical lesions in control animals similarly injected with nonimmune serum or saline. The failure of passive immunization to provide complete protection was evident in the development of the atypical lesions, and in the demonstration of disseminated infection in the tissues of 3 of the 4 surviving animals 7 mo. after challenge. The possibility that incomplete protection was due to insufficient immune serum levels, intracellular location of T. pallidum and/or cell-mediated mechanisms is discussed.