The Retinoblastoma (Rb) phosphothreonine 821Polyclonal Antibody from MyBioSource.com is a Rabbit Polyclonal antibody to p105-Rb, pRB, and RB1. This antibody recognizes Human antigen. The Retinoblastoma (Rb) phosphothreonine 821Polyclonal Antibody has been shown to work in the following applications: Western Blot.