Monoclonal anti-T12 antibody as therapy for renal allograft rejection.

: Nineteen renal allograft recipients experiencing rejection were infused with monoclonal mouse anti-human T12 directed to a T lymphocyte differentiation antigen expressed on mature post-thymic cells. Patients were offered this therapy as an alternative to high-dose methylprednisolone after diagnosis of an acute rejection episode within 3 months of transplantation. Seven patients had clear-cut reversals of rejection activity within the 10-day period of treatment. Four additional patients had delayed responses in association with acute tubular necrosis and/or cyclosporine toxicity, and they received other therapies according to protocol when anti-T12 alone had not caused a response after 5 days. All but one of these responding patients have been free of subsequent acute rejection over a 1-15 month follow-up period. Treatment failures appear to be related to the presence of allo-antibody-mediated vasculitis. Therapy was well tolerated. These preliminary studies have revealed the existence of a T12 negative subpopulation of extrathymic T cells, usually undetectable in peripheral blood.