Antibody to doublet immunoprecipitates telomerase activity. Affinity-purified rabbit polyclonal antiserum raised against the doublet was used to immunoprecipitate telomerase activity as in Fig. 2A, and the lysate, supernatant, wash, and pellet were analyzed for telomerase activity by TRAP. PI, preimmune serum; I, immune serum; +RN, RNase A-inactivated lysate.