PRODUCTION OF TL ANTIBODY BY MICE IMMUNIZED WITH TL^- CELL POPULATIONS : A POSSIBLE ASSAY FOR THYMIC HORMONE

TL^- mice make TL antibody when immunized with spleen or bone marrow cells from TL⁺ donors, despite the fact that these cells do not express TL antigen. This has been shown to depend on maturation of TL^- precursors, contained in the inoculum, into TL⁺ cells under influence of the recipient's thymus; the differentiated TL⁺ cells then evoke production of TL antibody.