Heightened Immunity and Susceptibility toward Cheek Pouch Heterografts of a Mouse Leukemia in Syrian Hamsters.

Heterotransplantation of 1.0 X IO7AK-4 cells of AKR mice into cheek pouches of normal and cortisone-treated adult Syrian hamsters resulted in measurable but tran sient growth; small vascular tumors which appeared at 5-7 days regressed completely by 10-14 days. Noncortisonized hamsters vigorously rejected second-set grafts, which failed to vascularize, in considerably less time, in either the previously exposed or contralateral pouch. Hamsters treated with cortisone during and following rejection of the first-set graft also vigorously rejected second-set grafts at 2 weeks following first-set grafting but accepted second-set grafts, in 50 per cent of the instances at 4-6 weeks, in either the previously exposed or contralateral pouch. This acceptance of second-set grafts was in contrast to the failure of hamsters pretreated with cortisone alone to support the growth of first-set grafts. Successful second-set grafts in cortisone-treated hosts grew progressively for 10-14 days, after which interval the grafts necrotized and ulcerated. Despite evidence of locally infiltrating cheek pouch tumors at death at 4-6 weeks, in no instance was dis seminated leukemia observed. Retransplantation of hamster-borne tumors to mice, however, resulted in selective death of AKR mice with disseminated disease, indicating retention of strain-specificity and the capacity of the cells to generalize. The possible relation between heightened susceptibility to AK-4 heterografts in the hamster pouch, and tumor homograft enhancement in the mouse is discussed, as is the significance of this study with respect to the concept of "immunological privilege"