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Journal of Experimental Medicine, Vol 179, 1215-1224, Copyright © 1994 by Rockefeller University Press
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HI Levitsky, A Lazenby, RJ Hayashi and DM Pardoll
Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Downregulation of major histocompatibility complex (MHC) class I expression is an important mechanism by which tumors evade classical T cell-dependent immune responses. Therefore, a system was designed to evaluate parameters for active immunization against MHC class I- tumors. Mice were capable of rejecting a MHC class I- tumor challenge after immunization with an irradiated granulocyte/macrophage colony- stimulating factor (GM-CSF) transduced MHC class I- tumor vaccine. This response was critically dependent on CD4+ T cells and natural killer (NK) cells, but minimally on CD8+ T cells. A strong protective response against MHC class I+ variants of the tumor could be elicited when mice were immunized with irradiated MHC class I+ GM-CSF-secreting tumor cells. This response required CD4+ and CD8+ T cells, and in addition, elimination of NK cells resulted in outgrowth of tumors that had lost expression of at least one MHC class I gene. Finally, class I MHC expression on the vaccinating cells inhibited the response generated against a MHC class I- tumor challenge. These results demonstrate that the host is capable of being immunized against a tumor that has lost MHC class I expression and reveal conditions under which distinct effector cells play a role in the systemic antitumor immune response.
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