The Activity of Tolerant Antileukemia Sera: I. In Vivo Effects¹

Neonatal Dutch rabbits were rendered immunologically tolerant to normal AKR/J mouse tissue. The subsequent immunization of these rabbits with the same types of tissues from AKR/J mice which had spontaneously developed a frank lymphatic leukemia produced antisera which were unique in having minimal mouse toxicity combined with strong antileukemia activity. Anti-normal tissue sera and antileukemia sera formed after the immunization of rabbits not pretreated with normal tissue as neonatals, or antisera from rabbits tolerant to normal tissue, immunized with normal tissue, differed markedly in their murine toxicity and antileukemia effects. Antibodies specific to leukemic antigens are implicated by this work.