REMOVAL OF BABOON AND HUMAN ANTIPORCINE IGG AND IGM NATURAL ANTIBODIES BY IMMUNOADSORPTION - RESULTS OF IN-VITRO AND IN-VIVO STUDIES

The safe and effective removal of xenoreactive antibodies in the perit ransplant period is Likely to be critical for the clinical application of xenotransplantation involving disparate donor species, such as the pig, In an effort to develop an improved method for antibody removal in xenotransplantation, we have studied reusable antihuman antibody (I g) columns in vitro and in vivo. Two types of columns were tested: (1) an antihuman Ig column containing polyclonal sheep antihuman IgG (hea vy- and light-chain-specific) conjugated to sepharose CL-4B (Ig-Theras orb), and (2) an antihuman Ig column using polyclonal antihuman IgM (m u chain-specific) conjugated to sepharose, Passage of human or baboon plasma through the Ig-Therasorb column resulted in 97.5% and 78.4% mea n reductions in total IgG and IgM, respectively, Reductions in total I gG and IgM correlated with lowering of antipig IgG (54-486 fold) and I gM (9-54 fold) antibody titers as assessed by pig endothelial cell ELI SA. The ability of the Ig-Therasorb to significantly reduce IgM may be attributed to the light chain specificity of this column. With the an ti-IgM column, marked reductions in total (82.6-83.9%) and antipig (27 -54 fold) IgM in human and baboon plasma occurred, while levels of tot al and xenoreactive IgG were slightly affected. Other than a dilutiona l effect, neither column resulted in significant reduction in albumin, fibrinogen, factor 5, and factor 8, Repeated in vivo use of either co lumn in baboons achieved reductions in IgG and IgM that closely follow ed the results of our in vitro studies. No subject morbidity or mortal ity occurred. Use of the Ig-Therasorb column with immunosuppression in two baboons receiving pig renal xenografts achieved sustained reducti ons in antipig antibodies and prevented hyperacute rejection, Subjects were sacrificed at 11 and 13 days posttransplant with functioning xen ografts and were found to have no evidence of vascular xenograft rejec tion, We conclude that anti Ig columns represent a safe and effective method for antibody removal, without several of the limitations of oth er antibody removal techniques. Also, columns appear to be safe for re peated antibody removal in the posttransplant period.