Description:
<jats:title>Abstract</jats:title><jats:p>A series of rat monoclonal antibodies (mAb) directed against the Thy‐1 molecule have been evaluated for their ability to stimulate immature (CD4<jats:sup>−</jats:sup>8<jats:sup>−</jats:sup>) murine thymocytes. CD4<jats:sup>−</jats:sup>8<jats:sup>−</jats:sup> thymocytes could be induced to proliferate by several anti‐Thy‐1 mAb provided that exogenous inteleukin 1 or interleukin 2 was provided. Apparently nonstimulatory anti‐Thy‐1 mAb could be rendered stimulatory if cross‐linked by a rabbit anti‐rat immunoglobulin reagent. Anti‐Thy‐1‐stimulated CD4<jats:sup>−</jats:sup>8<jats:sup>−</jats:sup> thymoctes were found to uniformly express CD3 but did not stain positively with F23.1, a mAb reactive with α/β T cell receptors utilizing the V<jats:sub>β</jats:sub>8 gene family. Immunoprecipitation analysis of such stimulated CD4<jats:sup>−</jats:sup>8<jats:sup>−</jats:sup> thymocytes indicated that they expressed a CD3‐associated heterodimer of 45 kDa/35 kDa most likely corresponding to the product of the γ and (putative) δ T cell receptor genes. Taken together, these data demonstrate that anti‐Thy‐1 mAb selectively activate a subset of CD4<jats:sup>−</jats:sup>8<jats:sup>−</jats:sup> thymocytes committed to the γ/δ T cell receptor lineage.</jats:p>