Effect of antioxidants on humoral immune responses, such as butylated hydroxytoluene (BHT), n-propyl gallate (PG) and dimethyl sulfoxide (DMSO) is suppression in vitro antibody production. These antioxidants all inhibited T-dependent B cell response, not T-independent and polyclonal B cell response. These data suggest that antioxidants suppress humoral immunity by suppression of regulation of T cells or action of macrophages on B cells, not by direct suppression of B cells. The other possible explanation for antioxidant action is the lack of T-B cell contact required for the triggering of the B cell response with T-dependent antigens.