Thymic involvement in memory responses after primary challenge with TNP-Ficoll in Xenopus laevis, the South African clawed toad

Memory to TNP-Ficoll in Xenopus laevis is demonstrable as a more rapid secondary response rather than an augmented response. While adult thymectomy abrogates ability to respond to both primary and secondary challenge with soluble TNP-Ficoll, memory to this antigen can be revealed in thymectomized animals by challenge with TNP-Ficoll on bentonite beads. Memory to TNP-Ficoll cannot be revealed by secondary challenge with TNP-LPS or TNP-RBC, but memory to TNP-LPS is revealed by TNP-Ficoll challenge. These results are consistent with the hypothesis that, whereas B1 cells (capable of responding to TI-2 antigens) can develop from a pool of B1 and B2 memory cells (generated in response to TD or TI-1 antigens), initial challenge with TI-2 antigen does not produce a pool containing both B-cell subsets.