Partial characterization of cell surface idiotypes on alloantigen-activated T lymphoblasts.

T lymphoblasts of specificity Lewis anti-DA, Lewis anti-BN, BN anti-DA and L.BN anti-DA were purified on Ficoll-Paque from mixed leucocyte cultures on day 5. Blasts were radiolabelled with iodine-125 by the lactoperoxidase method and lysed by the aid of Nonidet P40. Idiotypic molecules were puried from the lysates by the use of anti-idiotypic antiserum of specificity anti-(Lewis anti-DA) and Staphylococcus aureus bearing protein-A. In this way, molecules with a molecular weight of 150,000 and 75,000 daltons could be isolated from Lewis anti-DA and L.BN anti-DA T lymphoblasts but no significant radioactivity was brought down by the same procedure from Lewis Lewis anti-BN or BN anti-DA T lymphoblasts. No additional molecules were detected on the lower molecular weight regions where light chains of Ig type as well as conventional products of the MHC genes would appear. The 150,000 dalton molecules are composed of two single polypeptide chains with a molecular weight of around 75,000 daltons. These data are in complete agreement with earlier results on antigen-binding, idiotypic receptors obtained from normal rat T lymphocytes.