Immunomodulation of human fetal cells by the fungal metabolite gliotoxin

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Abstract
Gliotoxin (GT) is a fungal metabolite that reduces the ability of murine macrophages to react immunologically in vitro. It is also capable of modulating the immunogenicity of murine bone marrow cells, so that the onset of graft-versus-host disease in fully allogeneic bone marrow chimeras is delayed. The present study examines the effect of GT on human fetal cells, both in terms of reduction of immunogenicity and toxicity. GT (10 g/ml) significantly decreased the responsiveness in mixed lymphocyte cultures of cells derived from human fetal pancreas, spleen, liver and bone marrow. This concentration of GT was, however, mildly toxic to explants of the pancreas, with a significant reduction in insulin secretion from this tissue during the first day of its organ culture, but not thereafter. GT-treated pancreatic explants were lighter and contained less insulin than the untreated controls 3 months after the tissue had been implanted beneath the renal capsule of nude mice. This difference was not apparent 3 weeks after transplantation into these animals. It is hypothesized that the immuno-modulating effect of GT (at a concentration less than 10 g/ml) may be of benefit in treating allografted human fetal pancreas before it is transplanted, as it has for murine adult bone marrow cells.