Special Property of the Cheek Pouch in Heightened Suscepti bility to Heterografts of a Mouse Leukemia* RICHARDA. ADAMS

Intravenous administration of 1.0 X IO7AK-4 cells or AKR spleen cells to normal Syrian hamsters (not conditioned with cortisone) resulted in heightened immunity to cheek pouch challenge of 1.0 X IO7AK-4 cells from 2 through 6 weeks following prior exposure. However, about 50 per cent of similarly exposed animals, concomitantly treated with 2.5 mg. cortisone acetate twice per week (starting from the time of prior exposure to the cells), supported the growth of subsequent cheek pouch-challenging inocula. Heightened immunity in noncortisonized hosts manifested itself as accelerated rejection and as failure of vascularization, or implantation, or both, of the challenging inocula. Heightened susceptibility in cortisone-treated hosts manifested itself as pro gressive growth for 15 days, followed by death with large, necrotic cheek pouch tumors at 4-6 weeks. Growing tumors did not disseminate but retained the capacity to do so upon retransplantation into the mouse strain of origin. The successful growth of second-set heterografts of AK-4 in cortisone-treated ham sters is demonstrated to be dependent upon a special property of the cheek pouch, by the failure of challenging subcutaneous implants to grow in suitably pretreated hosts, and by the successful growth of tumors transplanted to heterotopically autografted cheek pouches. Failure of challenging inocula to grow in suitably pretreated animals challenged in autografted full-thickness skin grafts indicates that successful growth in heterotopically grafted pouches is not a function of the surgical grafting procedures. Transferrability of the growth-supporting property of the cheek pouch with the heterotopically grafted cheek pouch indicates that the property is inherent in the cheek pouch tissues. "Immunological privilege" of the cheek pouch is discussed, and the