IMPROVED LONG-TERM GRAFT OUTCOME IN LUNG-TRANSPLANT RECIPIENTS WHO HAVE DONOR ANTIGEN-SPECIFIC HYPOREACTIVITY

We have shown that in renal transplant recipients the development of i n vitro donor antigen-specific hyporeactivity correlates with improved long-term graft outcome. Donor antigen-specific hyporeactivity is det ermined by in vitro mixed lymphocyte culture assays with recipient cel ls used as responder cells and homozygous typing cells as stimulator c ells. Hyporeactivity is defined as a decreased response to stimulation by specific homozygous typing cells that define donor antigens, where as response to homozygous typing cells defining third-party antigens r emains unchanged. We tested 23 lung transplant recipients at least 1 y ear after transplantation to determine if donor antigen-specific hypor eactivity and the corresponding improved graft outcome were organ spec ific. Of these 23 recipients, eight had donor antigen-specific hyporea ctivity; they demonstrated a trend toward a lower incidence of late ac ute rejection episodes (one rejection episode in one patient) versus t he 15 recipients who remained responsive to donor antigens (11 rejecti on episodes in six patients). No recipients with donor antigen-specifi c hyporeactivity have been diagnosed with obliterative bronchiolitis, unlike six recipients who remained responsive to donor antigens (0% ve rsus 40%; p = 0.058). We conclude that immune regulation, as evidenced by donor antigen-specific hyporeactivity, correlates with improved gr aft outcome for lung transplant recipients and may even provide immuno logically based criteria for selecting candidates whose immunosuppress ion might be reduced successfully.