The effect of 3,6-bis(2-piperidinoethoxy) acridine trihydrochloride (CL 246, 738) on acute graft vs host reactions in mice.

3,6-Bis (piperidinoethoxy) acridine trihydrochloride (CL 246, 738) prevented the development of graft vs host (GVH) disease in normal BDF1 mice injected with C57BL/6 parental spleen cells. A single oral dose (50 mg/kg) given on day 0 or day -1 of GVH induction prevented the day 10 GVH-associated suppression of mitogen responsiveness and IL-2 production. The drug was ineffective if given later (days 3-7) in the reaction. The protective effect of CL 246,738 was neutralized by injecting drug-treated GVH mice with antibody to asialo GM-1 (ASGM-1). This suggested that the protective mechanism was not due to a direct effect of the drug on donor cells but rather was achieved indirectly through the activation of host ASGM-1+ cells which then rejected donor lymphocytes. This hypothesis was supported by immunofluorescence which showed that the donor-host chimerism seen in control GVH mice was not found in drug-treated GVH mice. Direct verification of this hypothesis was provided by data which showed that the transfer of CL 246, 738-activated large granular lymphocytes from normal F1 mice can prevent donor-induced immunosuppression in GVH mice. The results suggest that CL 246,738 is a potent immunostimulant which can boost natural resistance of normal unirradiated mice.