Schistosoma mansoni: antigen-presenting cells emigrating from skin exposed to attenuated cercariae activate lymphoid cells and transfer protection in C57B1/6 mice.

C57B1/6 mice develop significant levels of protection to a challenge infection after percutaneous exposure to irradiated Schistosoma mansoni cercariae. Although some circumstantial evidence has suggested that antigen-presenting cells (APCs) within the skin play a role in priming anti-schistosomula effector mechanisms, no direct evidence has been presented. In this study, we describe efforts to directly test whether skin-resident APCs exposed to irradiated cercariae are capable of mediating responses consistent with previously proposed mechanisms associated with delayed-type hypersensitivity reactions. We demonstrate that a population of APCs emigrates from the skin after percutaneous vaccination and that these cells are able to induce proliferation of S. mansoni-specific lymphocytes. We describe our experiments conducted to confirm that proliferation is dependent on major histocompatibility complex (MHC) Class-II interactions and cell-to-cell contact between APCs and lymphocytes. Immunohistological staining of emigrating cells revealed a population of large MHC Class-II+ cells with a morphology characteristic of mature dendritic cells. On recovery and adoptive transfer into naive mice, these cells demonstrated the ability to mediate protection to a challenge infection at levels similar to those in percutaneously vaccinated controls. This confirms that cutaneous APCs can initiate anti-schistosomula effector mechanisms in C57B1/6 mice after percutaneous vaccination.