Reduction of complement factor H binding to CLL cells improves the induction of rituximab-mediated complement-dependent cytotoxicity

Leukemia. 2013 Nov;27(11):2200-8. doi: 10.1038/leu.2013.169. Epub 2013 Jun 13.


A main effector mechanism of rituximab (RTX) is the induction of complement-dependent cytotoxicity (CDC). However, this effector function is limited, because CLL cells are protected from complement-induced damage by regulators of complement activation (RCAs). A prominent RCA in fluid phase is factor H (fH), which has not been investigated in this context yet. Here, we show that fH binds to CLL cells and that human recombinant fH-derived short-consensus repeat 18-20 (hSCR18-20) interferes with this binding. In complement-based lysis assays, CLL cells from therapy-naive patients were differently susceptible to RTX-induced CDC and were defined as CDC responder or CDC non-responder, respectively. In CDC responders, but notably also in non-responders, hSCR18-20 significantly boosted RTX-induced CDC. Killing of the cells was specific for CD20(+) cells, whereas CD20(-) cells were poorly affected. CDC resistance was independent of expression of the membrane-anchored RCAs CD55 and CD59, although blocking of these RCAs further boosted CDC. Thus, inhibition of fH binding by hSCR18-20 sensitizes CLL cells to CDC and may provide a novel strategy for improving RTX-containing immunochemotherapy of CLL patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal, Murine-Derived / pharmacology*
  • Antibody-Dependent Cell Cytotoxicity / immunology*
  • Antineoplastic Agents / pharmacology
  • Blotting, Western
  • Complement Activation / immunology*
  • Complement Factor H / immunology
  • Complement Factor H / metabolism
  • Cytotoxicity, Immunologic / immunology*
  • Flow Cytometry
  • Humans
  • Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy
  • Leukemia, Lymphocytic, Chronic, B-Cell / immunology*
  • Leukemia, Lymphocytic, Chronic, B-Cell / metabolism
  • Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
  • Prognosis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism
  • Rituximab
  • Tumor Cells, Cultured


  • Antibodies, Monoclonal, Murine-Derived
  • Antineoplastic Agents
  • Recombinant Proteins
  • complement factor H, human
  • Rituximab
  • Complement Factor H