AN ATTEMPT TO PRODUCE LOW-ZONE TOLERANCE TO TISSUE ALLOANTIGENS

The injection of low doses of a transplantation antigen rendered water soluble with the enzyme phospholipase A failed to prolong the survival of skin grafted across an H-2 barrier 1, 4, or 12 days after treatment or to suppress the production of hemagglutinating antibodies following grafting. Skin grafted 1 day after i.v. injection of 0.5 mg and 12 days after the injection of 5.0 mg of phospholipase A-digested lipoprotein showed the longest survivals. Injection of 10 µg and 50 µg were followed by accelerated rejection, particularly when grafted 12 days after injection. Skin grafted 12 days after the injection of 0.5 mg and 1.0 mg was also rejected in an accelerated fashion. The degree of acceleration obtained utilizing the i.v. route of administration was less than that observed in earlier studies utilizing the s.c. route. No correlation could be drawn between the speed of rejection and the strength of the hemagglutinin response following grafting. Possible reasons for the failure to produce low-zone tolerance are: the choice of an inappropriate time-dose schedule, the utilization of an inappropriate antigen, or the inapplicability of low-zone tolerance to the production of cellular immunity. © 1969 by The Williams and Wilkins Co.