Activated neutrophils as effector cells for bispecific antibodies.
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Biomedical subjects
Publications and source records attributed to T Valerius.
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Antibody-based therapy is a new treatment option for selected tumor patients. Today, human IgG(1) is the most widely used isotype, because it effectively activates human complement, recruits NK cells for ADCC, and has an extended plasma half life. In recent work, however, neutrophils--the most populous cytotoxic cells in humans--were more effectively recruited by human IgA than by IgG antibodies. IgA antibodies may have the additional advantages of forming natural dimers with improved signaling capacity on tumor cells, and being actively transported into mucosal secretions with the potential for improved targeting of certain carcinomas from the luminal surface.
BACKGROUND: Bispecific antibodies--consisting of a F(ab')-fragment derived from a monoclonal antibody against a tumor epitope as well as of another antibody against a cytotoxic trigger molecule on immune effector cells--can improve the effectiveness of antibody-based tumor therapy. MATERIALS AND METHODS: We used bispecific antibodies with one specifity against the EGF-receptor, which is overexpressed on the majority of renal cell carcinomas, and another specifity against Fc receptors on human leukocytes (Fc gamma RI/CD64; Fc gamma RIII/CD16 and Fc alpha RI/CD89). As source of effector cells, whole blood from patients treated with G-CSF, GM-CSF or IL2/IFN-alpha was used in 51Cr- release assays using various renal cancer cell lines as tumor targets. Further experiments with Percoll-isolated granulocytes or mononuclear cells from the same donors were performed in order to identify the active effector cell populations. RESULTS: Compared with conventional monoclonal EGF-R directed antibodies (murine IgG2a, humanized IgG1), bispecific antibodies induced significantly enhanced cytotoxicity. Highest amounts of tumor cell killing were observed using whole blood from patients treated with G-CSF or GM-CSF in combination with an [Fc alpha RI x EGF-R] bispecific antibody. Under these conditions, granulocytes constituted the most active effector cell population. CONCLUSION: The combination of myeloid growth factors and bispecific antibodies offer a promising new approach for the treatment of advanced renal cell carcinoma.