Recombinant DNA produced human IL-2, injected in vivo, will substitute for carrier priming of helper function in the South African clawed toad, Xenopus laevis.

The studied included in this report tested the ability of a recombinant DNA produced human lymphokine (rIL-2) to serve as a substitute for the carrier priming required for the in vivo generation of anti-hapten responses, in young adults of Xenopus laevis, the South African clawed toad. Heterologous erythrocyte carriers were used. Immune reactivity was monitored with hapten-specific antigen binding cells (ABC) in spleen cell suspensions, 8 days after injection i.p. of trinitrophenylated sheep erythrocytes (TNP-SRBC) or rIL-2 or the two together. No substantial anti-hapten responses were generated by either TNP-SRBC or rIL-2 alone. However, a greatly (9X) enhanced anti-TNP response was produced after co-injection. By varying the time between injection of the rIL-2 and the TNP-SRBC challenge, it was found that the effectiveness of this mediator would last for up to three hours in this animal. When rIL-2 was co-injected with an optimal priming dose of SRBC, two days prior to TNP-SRBC challenge, it did not enhance the level of helper function generated by carrier priming. Therefore, it is likely that the rIL-2 acts on the same cells affected by carrier priming which is maximally efficient in this regard. Thus, cells, which participate in the generation of helper function in this primitive species, are sensitive to human rIL-2. The universality of an immune regulatory molecule of this kind is considered.