Orthotopic transplantation of alogeneic canine conjunctiva

In previous papers it has been shown that simultaneous transplantation of conjunctiva to the corneal-scleral region, and skin to the inside of the pinna will afford good opportunities to follow both the onset and the terminal phase of the allograft reaction. It has also been stated that conjunctiva grafted alone will have a longer survival time (12.1 days), than when grafted simultaneously with skin (7.5 days). In order to find out whether the localization to the corneal-scleral region per se had anything to do with this prolongation of the survival time, conjunctiva was grafted in 8 dogs to the palpebral surface of the nictitating membrane, i.e. more peripherally in the type used as grafts in previous experiments were weighed and examined histologically to compare the "tissue doses" --quantitatively and quanlitatively--transferred to the recipient when transplanting conjunctiva plus skin, or conjunctiva alone. Conjunctiva alone grafted to the nictitating membrane had a mean survival time of 10.5 days which does not significantly differ from the mean survival time of conjunctiva grafted to the cornealscleral region. Various possible reasons for the significantly prolonged survival time of conjunctiva alone, compared with that of conjunctiva when grafted with skin, are discussed in some detail. The author suggests that the most likely explanation of the prolonged survival time of the conjunctival grafts applied alone is that this operation means transfer of an antigen dose so low that the mobilization of the immune defence system is delayed.