ANTITUMOR EFFECTS OF INTERFERON IN MICE INJECTED WITH INTERFERON-SENSITIVE AND INTERFERON-RESISTANT FRIEND-ERYTHROLEUKEMIA CELLS .8. ROLE OF THE IMMUNE-SYSTEM IN THE INHIBITION OF VISCERAL METASTASES

DBA/2 mice were injected i. v. with IFN α/β‐resistant 3C18 Friend erythroleukemia cells (FLC) which metastasize to the liver and spleen. IFN α/β treatment of FLC‐injected mice increased their survival time and these mice developed a resistance to a second challenge with FLC. The efficacy of IFN α/β in increasing the survival time was compared between normal immunocompetent and immunodeficient mice. The antitumor action of IFN was markedly reduced or abolished in newborn DBA/2 mice, in adult athymic nu/nu and beige DBA/2 mice, and in BALB/c scid/scid mice. To determine the phenotype of the effector cells involved, FLC‐injected DBA/2 mice were treated with antibodies to asialo‐GMI, CD4, or CD8 antigens, or with cyclosporin A or silica. IFN α/β treatment proved much less effective in these mice, indicating that a variety of effector cell types participated in the IFN‐induced suppression of visceral metastases. Thus, an intact immune system appears to be essential to obtain optimal therapeutic effects of IFN α/β in this experimental model. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company