Immunoglobulin G‐mediated regulation of the murine immune response to transfused red blood cells occurs in the absence of active immune suppression: implications for the mechanism of action of anti‐D in the prevention of haemolytic disease of the fetus and newborn?

Abstract

SummaryAnti-D has been widely and effectively used in Rhesus blood group D negative mothers for the prevention of haemolytic disease of the fetus and newborn; its mechanism of action however, often referred to as antibody-mediated immune suppression (AMIS), remains largely unresolved. We investigated, in a murine model, whether active immune suppression or clonal deletion mediated by anti-red blood cell (RBC) immunoglobulin G (IgG) could explain the phenomenon of AMIS. Transfusion of IgG-opsonized foreign RBCs (i.e. AMIS) strongly attenuated antibody responses compared to transfusion of untreated foreign RBCs. When the AMIS-mice were subsequently transfused with untreated RBCs, no immune suppression was observed at 5 and 35 days after AMIS induction; in fact, the mice responded to retransfusion with untreated RBCs in a manner that was characteristic of a secondary immune response. When IgG-opsonized RBCs were transfused concurrently with untreated RBCs, a dose-dependent reduction of the antibody response was observed. This work suggests that the attenuation of the antibody responsiveness by anti-RBC IgG is not associated with active immune suppression or clonal deletion at either the T-cell or B-cell level; rather, the effect appears more characteristic of B-cell unresponsiveness to IgG-opsonized RBCs. These results may have implications for the understanding of the mechanism of action of anti-D in haemolytic disease of the fetus and newborn.

Transfusion of antibody‐opsonized red blood cells results in a shift in the immune response from the red blood cell to the antibody in a murine model

“…Tetanus toxoid and diphtheria toxoid used for the enzyme‐linked immunosorbent assays (ELISAs) were purchased from Listlabs‐Cedarlane (Hornby, Ontario, Canada). IgG anti‐SRBC and IgG anti‐NP were prepared and purified from sera from BALB/c mice hyperimmunized against SRBC‐ or NP 30 ‐keyhole limpet hemocyanin (Biosearch Technologies) and IgG purified using protein G‐agarose column chromatography (Pierce, Rockford, IL) as detailed elsewhere 28 …”

“…There is evidence that the AMIS effect may be restricted to B cells, because T‐cell responses can occur under AMIS conditions 18,20,24‐28 . Furthermore, AMIS may not be related to tolerogenic mechanisms because a subsequent antigen challenge after complete AMIS induction resulted in an antibody response 29,30 …”

IgG-Mediated Immune Suppression to Erythrocytes by Polyclonal Antibodies Can Occur in the Absence of Activating or Inhibitory Fcγ Receptors in a Full Mouse Model

“…Although the transfusion of xenogenic SRBC has been widely used to study IgG-mediated immune suppression mechanisms by us (12,13,(18)(19)(20)(21) and others (16,(22)(23)(24)(25), validation against an allogenic mouse model is essential as SRBC do not meaningfully enter the mouse circulation and also contain inflammatory ligands and the actual Ags on the SRBC have not been definitively established (3,26). Contrary to the transfusion of allogeneic mouse RBC that circulate with a normal life span (27,28), SRBC are cleared from circulation within a few hours (29,30).…”

Transfusion of IgG-Opsonized Foreign Red Blood Cells Mediates Reduction of Antigen-Specific B Cell Priming in a Murine Model

“…Because the APC function of B cells depends on successful priming (24,25), B cell priming is probably either absent, down-regulated, or otherwise changed under AMIS conditions. We and others have observed that immunization at early time points after AMIS induction did not lead to suppression, but rather generated a secondary-like Ab response (19,33,34). This secondary-like response, a priori, excludes B cell anergy, B cell clonal deletion, or B cell clonal silencing as likely mechanisms for the observed lack of Ag-specific B cell APC function in vitro.…”