Development of synthetic immunotoxin that can enable ABC incompatible transplantation and xenotransplantation.

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The establishment of a novel method for persistent elimination of B cells responding to transplantation associated carbohydrates : We have demonstrated that B cells bearing receptors that recognize blood group A carbohydrates are found exclusively in the sIgM^+ CD11b^+ CD5^+ B-1 subset in the peripheral blood of humans with blood group O or B. Some reports suggest that the segregation to B-1 cells probably occurs via Ig gene rearrangement on stimulation with thymus-independent type 2 antigens. We have proved that cyclosporin A (CsA) and Tacrolimus (Tac) blocks such segregation to B-1 cells, although CsA has no effect on Ab-producing cells or differentiated B-1 cells. Based on these facts, we hypothesize that the specific elimination of both Ab-producing cells and differentiated B-1 cells with anti-A/B specificity and subsequent CsA/Tac therapy might lead to the long lasting inhibition of anti-A/B Ab production in ABO-incompatible organ transplantation. Balb/c mice resemble humans with … More blood group O or B in that the mice have natural Abs against human blood group A carbohydrates in their sera. B cells bearing receptors that recognize these A carbohydrates in mice also belong to the CD5^+ CD11b^+ B-1 subset. The ability of synthetic A carbohydrates (GalNAcα1-3Fucα1-2Gal) conjugated with BSA and rabbit anti-BSA Abs to deplete anti-A IgM-producing cells was studied in vitro. The Balb/c mice were first injected with A-BSA and then with anti-BSA Abs after 6 hours. In mice that received the injection of A-BSA/anti-BSA Abs, the serum levels of anti-A IgM reduced by day 14. However, immunization with human A RBCs on day 14 resulted in an increase in the serum levels of anti-A Abs. In contrast, when combined with the CsA treatment and treatment with A-BSA/anti-BSA Abs, the serum levels of anti-A Abs were persistently undetectable in the mice even after the immunization. These results are consistent with the hypotheses that treatment with A-BSA/anti-BSA Abs temporally depletes B cells responding to A determinants, and that CsA/Tac treatment prevents the replenishment of these cells. The establishment of a model for analyses of B cells responding to N-glycolylneuraminic acid : The presence in humans of natural antibodies directed against N-glycolylneuraminic acid (NeuGc) epitopes on pig vascular endothelium may provides another barrier in xenotransplantation, as antibody-antigen binding leads to rejection. There has been no animal model for analyses of B cells responding to NeuGcso far. We have established a in vivo model utilizing NeuGc-deficient mice. Less