STEPWISE INCREASE IN TRANSPLANTATION IMMUNITY AS A FUNCTION OF CUMULATIVE CELL DOSAGE

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Abstract
Separate groups of CBA/Jax mice were preimmunized with A/Jax splenic cells; 1, 3, 5, 7 and 9 intraperitoneal injections of 3000 ceils each were given at 4 day intervals. Skin homografts made in each recipient group on the 7th day after the last splenic cell injection showed a curtailed survival time proportional to the previous dose of A-line splenic cells. The MST''s ranged from 98 [plus or minus] 0.5 days in the 3000 ceil group to 7.9 [plus or minus] 0.8 days in the 27,000 cell group. A/Jax skin homografts on uninjected, adult, CBA/Jax mice had an MST of 10.8 [plus or minus] 0.8 days. The MST''s plotted as a curvilinear function of cumulative splenic cell dosage. It is estimated that a maximal immunity reflected in an MST of about 6 days would have required multiple intraperitoneal injections totaling about 50,000 cells, whereas at least several times as many splenic cells given in a single dose would be needed to produce a comparable immunity. A graded immune response to successive low doses of transplantation antigens is revealed by the present findings.