IMMUNE-COMPLEXES IN EXPERIMENTAL SYPHILIS - A METHODOLOGIC EVALUATION

Sustained antigenic stimulation following i.v. infection of rabbits with Treponema pallidum results in antibody responses and the formation of immune complexes. Complexes in > 300 sera from normal rabbits and from animals with experimental syphilis were measured by [human lymphoblastoid] Raji cell and polyethylene glycol-complement consumption assays. Profound increases in both the incidence and levels of immune complexes were seen between the 3rd and 7th weeks of infection. Single radial immunodiffusion studies revealed moderate increases in Ig levels and depression of C3 levels during the 3rd and 4th weeks of infection. Penicillin treatment was followed by normalization of C3 levels and clearance of immune complexes. Lower levels of complexes in the sera of intradermally infected rabbits and the absence of immune complexes in intratesticularly infected animals suggest that immune complexes in the circulation may be related to the extent and severity of cutaneous involvement.