TARGETING OF NK-LIKE T IMMUNOLOGIC EFFECTOR CELLS AGAINST LEUKEMIA AND LYMPHOMA CELLS BY REVERSE ANTIBODY DEPENDENT CELLULAR CYTOTOXICITY

Lefterova, A. Märten, P. Buttgereit, S. Weineck, C. Scheffold, D. Huhn, I.G.H. Schmidt-Wolf

Rheinische Friedrich-Wilhelms-Universität, Bonn; Virchow-Klinikum, Humboldt-Universität, Berlin, Germany and Bone Marrow Transplantation Program, Stanford University Medical Center, Stanford, CA

Running Title: Preincubation of leukemia cells with anti-CD3

ABSTRACT

Recently, highly efficient NK-like T immunologic effector cells termed cytokine-induced killer (CIK) cells have been described. Most interestingly, CIK cells have been shown to eradicate established human lymphoma cells in a SCID mouse xenograft model in vivo. Our study was aimed at increasing the sensitivity of leukemia and lymphoma cells to CIK cells. In particular, we were interested in targeting CIK cells to leukemia and lymphoma cells via reverse antibody dependent cellular cytotoxicity (ADCC). Binding of an anti-CD3 monoclonal antibody to CIK cell cultures derived from patients with lymphoma was demonstrated using flow cytometry. For the target side, several B cell lines were found to express CD19 on the cell surface. There was an impressive increase in sensitivity to CIK-mediated lysis of various lymphoma and leukemia cell lines by preincubation of the targets with a monoclonal antibody against CD3. This increase could be partially blocked by a preincubation with anti-CD16 (Fc receptor III) and anti-CD32 (Fc receptor II) antibodies. These data suggest that the increase in cytotoxic activity is due to Fc receptor-mediated antibody binding. Cytotoxic activity could be further increased by addition of an anti-CD28 antibody in addition to anti-CD3. Finally, there was a further increase in sensitivity to CIK-mediated lysis of CD19+ malignant cells using the bispecific OKT3xHD37 antibody with specificity against CD3 and CD19. Interestingly, preincubation of malignant cells with an anti-CD3 monoclonal antibody followed by addition of the bispecific OKT3xHD37 antibody led to a further increase of cytotoxic sensitivity as compared to addition of the bispecific antibody alone. In conclusion, our data suggest that cytotoxic activity of immunologic effector cells can be increased not only by the use of the bispecific antibody OKT3xHD37 in vitro but as well by preincubation of CD19+ leukemia and lymphoma cells with a monoclonal antibody against CD3. In addition, the immunostimulatory effect of the bispecific antibody OKT3xHD37 can be further increased by addition of a monoclonal antibody against CD3. Keywords: monoclonal antibody, leukemia, lymphoma, CD3, CD19; ADCC