CARDIAC ALLOGRAFT UNRESPONSIVENESS USING A POSTTRANSPLANT STRATEGY - CHARACTERIZATION OF THE GRAFT INFILTRATE

We evaluated a combined posttransplant strategy using antilymphocyte s erum (ALS) at; time of engraftment followed by low dose total lymphoid irradiation (TLI) and donor bone marrow cell (BMC) inoculation admini stered either intrathymically (IT) or intravenously (IV) in the vigoro usly rejecting strain combination DA into Lew recipients, Allograft su rvival was significantly prolonged with administration of ALS in combi nation with TLI and IT (105 +/- 28.6 days) or IV (106.8 +/- 28.6 days) BMC compared to administration of ALS combined with either TLI (17.8 +/- 0.4 days) or BMC (9.0 +/- 0.0 days), or TLI combined with BMC (11. 5 +/- 0.5 days) (P < 0.0001, experimental vs control animals). There w as no difference in survival between those animals who underwent IT or IV BMC inoculation. Third-party (WF) BMC inoculation did not signific antly prolong allograft survival (10.0 +/- 1.0 days). A mild to modera te cellular infiltrate was present in allograft tissue after 100 days. To further characterize these cells, cytokine mRNA expression in allo graft tissue (>100 days posttransplant) was evaluated using nonisotopi c in situ hybridization. A similar cytokine profile was demonstrated i n allograft tissue compared to naive and isograft tissue, except for a slight increase in IL-2 (P < 0.02, control vs IV BMC; P = NS, other g roups). In summary, unresponsiveness was induced in a high-responder s train combination using a combined posttransplant strategy of ALS, TLI , and donor antigen either IT or IV. The cytokine profile of the graft infiltrating cells was similar to that of normal tissue. Unresponsive ness may be the result of functional inactivation of these cells. (C) 1996 Academic Press, Inc.