The role of circulating antibody in the control of antibody synthesis: mechanism for the suppressive effect of passive antibody on active antibody synthesis

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?

Anti-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.

Antibody against CD20 in patients with B cell malignancy

Cancer patients may make antibodies against antigens on the surface of their malignant cells due either to the expression of unique antigens or to dysregulated responses to self antigens. Patients with B cell malignancy frequently produce autoantibodies and may therefore be a source of immunoglobulin genes for the production of phage display antibody libraries directed against tumour-associated antigens. Patients with autoimmune disease have circulating antibodies against lymphocyte surface antigens, and may also provide a good starting point for the production of a library of lymphocyte-reactive antibody structures. In this study, plasma and serum samples from patients with B cell malignancy or Sjogren's syndrome and from healthy controls were screened for antibodies against the B cell membrane antigens CD20. While the majority of samples showed very low reactivity, some individuals did show significant and reproducible binding to CD20. To identify a good donor for library construction, it would be advisable to screen donors for antibody against the antigens of interest.

Quantitation of purified monoclonal antibody needed to prevent HSV-1 induced stromal keratitis in mice

A purified IgG2a monoclonal antibody with a neutralizing titer of 10(4) and specificity for gD was evaluated for its therapeutic potential in a murine ocular infection model. BALB/c mice, infected on the scarified cornea with 10 times the HSV-1 strain RE concentration needed to produce severe and persistent stromal opacity, were given a single inoculation of antibody intraperitoneally 24 hours later. The animals were then followed for corneal disease development. Antibody, at concentrations as low as 10 micrograms per mouse, was strikingly effective at preventing corneal opacity. Furthermore, the corneas, once clear, remained clear whereas the controls developed +3 to +5 stromal disease which was still present 60 days post-infection. Animals that had been treated and recovered from infection were resistant to subsequent HSV-1 challenge on the opposite cornea. These results demonstrate the therapeutic potential of systemically administered microgram quantities of anti-gD antibody.