Human anti-idiotypic antibodies can be good immunogens as they target Fc receptors on antigen-presenting cells allowing efficient stimulation of both helper and cytotoxic T-cell responses

Anti-idiotypic antibodies that mimic tumour-associated antigens can stimulate anti-tumour T-cell responses. In this article, we have studied the role of pc in the presentation of T-cell epitopes by 2 anti-idiotypic antibodies, 105AD7 and 708, The human monoclonal antibody 105AD7, which mimics CD55, stimulated strong in vitro T-cell proliferation, gamma IFN secretion and redirected cytotoxicity in unprimed T cells from healthy donors. However, removal of the pc region of the anti-idiotype reduced the sensitivity of the assay 1,000-fold, as did inhibiting Fc uptake of the anti-idiotype by an excess of human IgG. The mouse anti-idiotype 708, which mimics CEA, failed to stimulate in vitro T-cell responses on unprimed T cells from healthy donors. However, when a human IgGI pc region replaced its mouse pc region, the anti-idiotype induced T-cell proliferation, gamma IFN secretion and redirected cytotoxicity in lymphocytes from unimmunised donors. Human anti-idiotypes are therefore good immunogens since they target pc receptors on antigen-presenting cells, allowing efficient stimulation of both helper and cytotoxic T-cell responses. The immunogenicity of other antiidiotypes may therefore be enhanced by human pc targeting of antigen-presenting cells. (C) 2001 Wiley-Liss, Inc.