Two annelid species (Family Lumbricidae), Lumbricus terrestris and Eisenia foetida reject orthotopic xenografts of integument. Ninety-three first-set and 46 second-set xenografts were exchanged. Both autografts and xenografts healed in during the first 24 hours, but subsequent events always led to destruction of xenografts at times ranging from 6–147 days. Gross signs of rejection began with pigment cell breakdown after 4–56 days. Soon after graft healing was initially achieved, acidophil cells infiltrated the graft-host contact zone. These phagocytic cells which probably originate from the lymph glands were more frequently associated with xenografts than autografts. Most second-set xenografts were destroyed by accelerated reactions; however a significant number showed the opposite effect, i.e., prolonged survival in relation to first-set grafts. Two important features emerged: (1) acute rejectors (11 days or less) of first-sets always showed prolonged survival of second-sets, whereas chronic rejectors generally showed accelerated destruction of repeat grafts; (2) short intervals (0–4 days) between first- and second-set grafts produced accelerated rejections, while extended intervals (33–71 days) led to prolonged survival of repeat grafts. Early onset of rejection of second-set grafts usually was followed by accelerated breakdown; conversely, late onsets of rejection were followed by prolonged survival. There was no apparent donor specificity in the rejection times of repeat grafts. This may reflect the predominance of many common species-specific xenogeneic antigens over alloantigens coupled with an apparent lack of precise host receptors for their detection. © 1968 by The Williams and Wilkins Co.
