Prolongation of skin allografts by recombinant tumor necrosis factor and interleukin-1

The hypothesis is that systemic administration of recombinant tumor necrosis factor-alpha (TNF-alpha) and/or recombinant interleukin-1 alpha (IL-1 alpha) can decrease the rejection of a skin allograft.

Tumor necrosis factor and IL-1 are pluripotent cytokine hormones that are central to the host immunologic response to foreign substances. Cytokine effects and toxicity may be reduced by systemic administration of recombinant cytokines. The authors previously have demonstrated that pretreatment with cytokines such as IL-1 or TNF can reduce the lethality of endotoxin (lipopolysaccharide), gram-negative sepsis, cancer cachexia, and oxygen toxicity.

Skin grafts from the tails of Balb/c mice were placed on the backs of C57Bl/6 mice. Mice were treated with daily intraperitoneal saline, recombinant m-TNF (Genentech, South San Francisco, CA) or h-IL-1 (Hoffman LaRoche, Nutley, NJ) from postgraft day 1 to postgraft day 28. Tumor necrosis factor and IL-1 high doses were chosen because they protected mice from the lethality of lipopolysaccharide. Animals were examined daily for toxicity and graft rejection. Graft survival was plotted in a Kaplan-Meier plot and analyzed by the log-rank test. Comparison of proportions was done using the Fisher's exact test.

Either TNF or IL-1 alone significantly prolonged skin graft survival compared with saline control. Furthermore, the combination of TNF and IL-1 prolonged skin graft survival longer than either cytokine alone. Mice on the highest dose TNF and IL-1 combination did not reject skin grafts during the 28-day treatment period. Significant toxicity was associated with cytokine treatment. Similar significant proportions of death occurred with IL-1 alone and the highest combination of TNF and IL-1.

Both TNF and IL-1 can be effective as suppressors of skin allograft rejection in mice.