Abstract
A synthetic nonadecapeptide (IL 19) derived from a sequence of v‐myb was covalently bound to haemocyanin and used for immunization. Anti‐IL 19 serum immunoprecipitated a 75 kDa protein in the lysate of metabolically labelled chicken and murine thymus cells. Presaturation of the serum with IL 19 abolished this immunoprecipitation, thus indicating that the product of c‐myb in both chicken and murine thymuses is the 75 kDa protein (p75c‐myb). Anti IL 19 serum also precipitated p48c‐myb) in the lysate of nonproducer myeloblasts.