Factors affecting the acquisition of resistance againstSchistosoma mansoniin the mouse. IV. The inability of T-cell-deprived mice to resist re-infection, and otherin vivostudies on the mechanisms of resistance

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Abstract
SUMMARY: CBA mice deprived of their T-cells by means of thymectomy and administration of rabbit anti-mouse thymocyte serum before a primary infection ofSchistosoma mansoni, failed to resist re-infection to the same extent as immunologically intact controls. However, little difference was made to the degree of resistance to re-infection acquired by thymectomizedS. mansoni-infected mice when the anti-thymocyte serum was administered after the primary infection and just before the challenge. Hydrocortisone acetate, when administered to primarily infected mice just before reinfection appeared to reduce the degree of acquired resistance, but the drug also had a schistosomicidal effect on the challenge-derived organisms. An attempt to specifically suppress the acquisition of resistance againstS. mansoniby administering serum from homologously infected, resistant donors before and during the course of a primary infection failed, and partial depletion of complement activity with cobra venom factor that was administered just before challenge also failed to affect resistance. Serum obtained from mice with chronicS. mansoniinfections and injected intradermally at the site of subsequent administration of a homologous percutaneous challenge infection failed to markedly inhibit maturation of the challenge in the recipient. Recipients of 3 ml of serum from heavily infected donors were also not significantly more resistant to challenge than untreated controls. However, isolated skin from heavily infected mice allowed fewer cercariae to penetrate and emerge transformed as schistosomula than did isolated skin from uninfected controls.