Effector and regulator functions of splenic and thymic lymphocytes in the clawed toad Xenopus

B cells in Xenopus, as characterized by surface immunoglobulin, nylon-wool adherence and ability to produce antibody in vitro, were found in both major lymphoid organs: 10-25% Ig-positive cells for spleen and 0.5-4% for thymus. The splenic and thymic B cells were able to produce specific antibody of both isotypes, IgM and low molecular weight (LMW) Ig (IgG equivalent). While for a T-cell-dependent antigen, DNP-KLH, both required T-cell help, thymic B cells for a specific antigen produced far more LMW Ig than splenic B cells. Thymic T cells had the same ability as splenic T cells to elicit an allogenic GvH, but with much less efficiency, probably as a result of fewer mature cells. In contrast to splenic T cells, thymic T cells provided little or no help for B cells and, in certain instances, demonstrated suppressor activity.