CD4+ T cell-mediated HER-2/neu-specific tumor rejection in the absence of B cells.

HER-2/neu (HER-2) is a cell surface proto-oncogene that is often overexpressed in carcinomas. Passive administration of anti-HER-2 antibodies in breast cancer patients has achieved promising results, but less is known about the role of antibodies in active immunization. We asked whether B cells/antibodies are needed for tumor immunity induced by plasmid (HER-2 and GM-CSF) immunization. HER-2 specific tumor immunity relied completely on both CD4+ and CD8+ T cells. IFN-gamma, and to a lesser extent IL-4, seemed to be crucial cytokines during tumor rejection. Protection was associated with production of anti-HER-2 IgG antibodies in B cell competent mice. After immunization, however, B cell-deficient mice rejected HER-2-expressing tumors as efficiently as control littermates. We conclude that T cells are the main effector cells in DNA vaccine induced immunity against HER-2 and that anti HER-2 antibodies are not necessary to elicit a protective anti tumor immune response in this model. Copyright 2003 Wiley-Liss, Inc.