Abrogation of spleen macrophage suppressive activity by 15-deoxyspergualin

We studied the immunomodulatory mechanism of 15-deoxyspergualin (DSG), a novel antitumor agent. To assess this, we used a mixed culture of antigen-primed lymph node cells (LNC) and spleen cells (SPC). In normal or untreated conditions, SPC suppressed the proliferative response of LNC to the antigens. In contrast, SPC from DSG-treated animals did not show any suppressive activity. This suppression was mediated by adherent cells in SPC but the suppression mechanism was recovered when DSG-treated spleen macrophages were reconstituted with control spleen nonadherent cells. These data suggest that DSG abrogates nonspecific suppressive activity of spleen cells by acting on both adherent and nonadherent cells.