Biologic response of B lymphoma cells to anti-CD20 monoclonal antibody rituximab in vitro: CD55 and CD59 regulate complement-mediated cell lysis

Abstract

The chimeric anti-CD20 MAb rituximab has recently become a treatment of choice for low-grade or follicular non-Hodgkin's lymphomas (FL) with a response rate of about 50%. In this report, we have investigated the mechanism of action of rituximab on 4 FL and 1 Burkitt's lymphoma (BL) cell lines, 3 fresh FL samples and normal B cells in vitro. Rituximab efficiently blocks the proliferation of normal B cells, but not that of the lymphoma lines. We did not detect significant apoptosis of the cell lines in response to rituximab alone. All cell lines were targets of antibody-dependent cellular cytotoxicity (ADCC). On the other hand, human complement-mediated lysis was highly variable between cell lines, ranging from 100% lysis to complete resistance. Investigation of the role of the complement inhibitors CD35, CD46, CD55, and CD59 showed that CD55, and to a lesser extent CD59, are important regulators of complement-mediated cytotoxicity (CDC) in FL cell lines as well as in fresh cases of FL: Blocking CD55 and/or CD59 function with specific antibodies significantly increased CDC in FL cells. We conclude that CDC and ADCC are major mechanisms of action of rituximab on B-cell lymphomas and that a heterogeneous susceptibility of different lymphoma cells to complement may be at least in part responsible for the heterogeneity of the response of different patients to rituximab in vivo. Furthermore, we suggest that the relative levels of CD55 and CD59 may become useful markers to predict the clinical response.

Blockade of bulky lymphoma‐associated CD55 expression by RNA interference overcomes resistance to complement‐dependent cytotoxicity with rituximab

“…(11) However, some researchers have reported that in vitro susceptibility to rituximab-induced CDC could not be predicted by the levels of CD55 protein in CLL cells, nor in vivo in FL and CLL patients. (12,13) On the other hand, Golay et al (27) have reported that relative levels of CD55 and CD59 may become useful markers to predict clinical responses. Overexpression of CD55 on some tumor cell lines and in colorectal carcinomas has been shown to be an indicator of poor prognosis.…”

Preconditioning regimen consisting of anti‐CD20 monoclonal antibody infusions, splenectomy and DFPP‐enabled non‐responders to undergo ABO‐incompatible kidney transplantation

“…For these patients, known as Ônon-respond-ersÕ, the current protocol offers new hope. Rituximab, a chimeric monoclonal antibody against human CD20 antigen, lyses CD20-positive cells in an antibody-and complement-dependent cell killing process (5). Although rituximab has been successfully used mainly in the field of hematological disorders, rituximab also has applications in the field of organ transplantation.…”

Control of Recombinant Monoclonal Antibody Effector Functions by Fc N‐Glycan Remodeling in Vitro

“…However, the relative contribution of CDC and ADCC to the therapeutic efficacy of recombinant Mabs is still in debate, though recent evidence suggests that the extent of CDC may be more indicative of therapeutic outcome (3). Furthermore, polymorphic variation in FcγRIIIa on NK cells (4,5) and studies on the involvement of complement inhibitors CD55 and CD59 (6,7) have been identified as factors influencing ADCC and CDC, respectively.…”