Tumor necrosis factor alpha and beta are polypeptide cytokines with a wide range of metabolic, immunologic, and inflammatory activities. TNF is known to participate in immune meditated injury of native lungs, but a role for TNF in mediating lung allograft rejection (AR) has not been established. In experiments reported here, we assessed the role of TNF in mediating lung AR in a rat model of lung transplantation (BN-->Lew) (RT1n-->RT1l). This model shows florid AR with all grafts completely destroyed by day 6 posttransplant. Graft pathology is characterized by massive lymphocytic infiltrates and hemorrhagic necrosis. Initially, 5 lung allograft recipients in each group were sacrificed on days 1 to 6 posttransplant. Allografts were removed, mRNA isolated, and Northern blotting or RT-PCR performed with blots probed with cDNAs or oligos specific for rat TNF-alpha cyclophylin and gamma-actin. Data were compared with syngeneic transplants (Lew-->Lew) and with normal controls. In addition, frozen lung allograft tissue was examined by indirect immunofluorescence, using antibodies specific for TNF. TNF-alpha mRNA levels were detectable on day 2 posttransplant, and peaked on days 6-7 posttransplant. IF studies showed TNF protein expression in mononuclear cells of rejecting allografts on day 3, peaking on day 6. Both TNF-alpha mRNA and protein levels correlated with maximal AR and hemorrhagic necrosis of grafts. Minimal TNF-alpha mRNA or protein was detected in syngeneic grafts or in contralateral native lungs. We than examined the ability of a rabbit polyclonal anti-TNF-alpha (7000 U/day) and anti-TNF-beta (5000 U/day) with 30% crossreactivity with rat TNF to modify the AR response. For each group, 4-5 left lung transplants were performed as described, and animals treated with anti-TNF-alpha, anti-TNF-beta, (anti-TNF-alpha + anti-TNF-beta) or with preimmune rabbit sera. All animals were sacrificed on day 6 posttransplant. Several pathological categories of inflammation were examined and scored (0-4), with a score of 0=0% involvement; 1=1-25% involvement; 2=26-50% involvement; 3=51-75% involvement; and 4=76-100% involvement. The mean and SD scores were obtained for all animals in the treatment categories mentioned above, and compared with preimmune-treated controls. Briefly, no differences in perivascular, peribronchial, or peribronchiolar cell infiltrates or edema were seen in treatment groups compared with controls. However, profound differences were seen in scores for vasculitis (1.6+/-0.5 vs. 3+/-0), (P< 0.0001), necrosis (0+/-0 vs. 3.0+/-0.71) (P<0.00001), and interalveolar hemorrhage (0.6+/-0.5 vs. 3.5+/-0.71) (P< 0.00001) in the (anti-TNF-alpha + anti-TNF-beta) treatment group compared with preimmune controls. Both anti-TNF-alpha and anti-TNF-beta treatment groups showed ameliorative effects on hemorrhagic necrosis and vasculitis, but not to the degree seen with the combination of both antibodies. These data suggest that TNF-alpha and beta are important mediators of lung AR in the rat. Although the intensity of cellular infiltration was not affected by anti-TNF therapy, there were profound reductions in vasculitis and hemorrhagic necrosis of the grafts.
