In this in vitro study, we compared the effects of zearalenone (ZEN) and some of its derivatives: a-zearalenol (a-ZOL), b-zearalenol (b-ZOL), and zearalanone (ZAN) on several peripheral blood mononuclear cell (PBMC) parameters: cytotoxicity, proliferation, as well as antibody and cytokine synthesis.