The regulatory role of the antigen-presenting cell in the development of hepatic immunopathology during infection with Schistosoma mansoni

A recent meeting held in Berlin (2nd Teupitz Colloquium) focused on the str iking ability of mononuclear phagocytes to either stimulate or inhibit a va riety of immune and immunopathological responses, and ascribed a distinctiv e phenotype to the antigen-presenting cells (APC) when exercising these opp osite functions. Th us, the phenotype and secretory profile of APC associat ed with 'classical activation' is achieved following stimulation with pro-i nflammatory cytokines such as interferon-gamma, and leads to full T cell ac tivation. On the other hand, it has long been known that T cells may also b e downregulated after interacting with certain APC. Many of such APC, origi nally simply thought to lack or have lost their stimulatory potential, are now thought to be in a state of 'alternative activation', which is associat ed with a different phenotype and secretory profile that can typically be i nduced with anti-inflammatory reagents, including the cytokines IL-4, IL-10 and IL-13. The purpose of this article is to analyze the immunopathologica l events that characterize the infection with Schistosoma mansoni in contex t with these distinct APC activation pathways. Available evidence from huma n and experimental data suggests that a desirable outcome of the APC du rin g this parasitic disease is to attain 'alternative activation', which serve s to promote and sustain a Th-2-polarized immune response associated with a more favorable anti-inflammatory and host-protective environment. Copyrigh t (C) 2000 S. Karger AG, Basel.