Identification of a T cell subset using a rabbit antibody raised against a T suppressor molecule

Rabbit antiserum to a unique component of an Ag-binding Ts-factor was generated by repeated immunization with purified 30-kDa protein isolated from Fd11 Ts factor (11). This antiserum (anti-p30) was shown to recognize cell surface determinants expressed on the Ts hybridomas Fd11 and A10 but not the fusion partner BW5147. Furthermore, this antiserum was shown to bind to approximately 4% of thymocytes and 10% of nylon wool-purified splenic T cells from all strains of mice tested. Sorting nylon wool-purified T cells from DBA/2 mice for the CD4+ and CD8+ subsets revealed both populations contained cells that bound anti-p30. In addition, when CD4-8- thymocytes were examined for anti-p30 labeling, it was found that about 30% of this enriched population also expressed p30 molecules. In a functional study, anti-p30 was able to neutralize the suppressive effects of Fd11 on a specific assay for in vitro antibody synthesis against ferredoxin.