Tolerance induction to a mammalian blood group-like carbohydrate antigen by syngeneic lymphocytes expressing the antigen, II: tolerance induction on memory B cells.

Induction of immune tolerance on memory B cells specific to transplantation carbohydrate antigens was studied in the experimental animal model of alpha1,3galactosyltransferase knockout (KO) mice, which lack the alpha-gal epitope (Galalpha1-3Galbeta1-4GlcNAc-R) and can produce the anti-Gal antibody against it. Memory anti-Gal B cells were generated by immunization of KO mice with pig kidney membranes (ie, xenogeneic cell membranes expressing an abundance of alpha-gal epitopes). Lymphocytes including memory anti-Gal B cells were administered into lethally irradiated KO mice, together with syngeneic wild-type (WT) lymphocytes expressing alpha-gal epitopes. Memory anti-Gal B cells were completely tolerized after being in vivo for 14 days with WT lymphocytes. This was indicated by the lack of anti-Gal immunoglobulin G (IgG) response following immunization with pig kidney membranes vs the extensive anti-Gal response in mice that did not receive WT lymphocytes. Tolerance induction was prevented if T cells were activated by alloantigens. This tolerance was highly specific to anti-Gal B cells and did not affect memory B cells with closely related specificity, such as B cells with anti-blood group A specificity. Tolerance induction on anti-Gal B cells was found to be time dependent and required more than 10 days of in vivo exposure of these B cells to WT lymphocytes. These observations suggest a novel method for induction of tolerance to transplantation carbohydrate antigens in humans, by in vitro transduction of autologous blood lymphocytes with an adenovirus containing the corresponding glycosyltransferase gene and administration of the transduced cells into the circulation after removal of natural antibodies to the antigen.