Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)

the nature of pathological lesions and was also numerically characterized by the so-called percent protection. It was established that: 1. Susceptible animals may be passively protected by antibodycontaining serum of rabbits infected by T. pisiformis eggs. 2. The degree of passive immunity induced by serum decreased with increase in interval between infection of donors and collection of serum. Sera obtained 28 and 30 days after infection induced a greater immunity (percent protection of 94,7 and 94,8 respectively) than those obtained after 59 or 62 days (percent protection of 54,6 and 65,2 respectively). 3. Passive immunity induced by serum was absolute in only a small number of cases but, compared to controls, serum-treated recipients showed a significant decrease in the number of developing cysticerci. 4. Cells obtained on day 59 after infection of donors induced a stronger immunity (percent protection of 84,7) than did cells obtained at 28 or 30 days (percent protection of 61 and 52,8 respectively

). Differences between pathological lesions in the livers of animals passively immunized by serum or cells and in those of controls imply that the immunity induced by humoral antibodies and cellular factors prevails in that phase of larval migration which extends until the emergence of the cysticerci from the liver. Results unequivocally indicate that the immunity induced in rabbits against T. pisiformis oncospheres can be transferred not only by circulating antibodies but also by lymphoid cells.