Sequential immunoprecipitation experiments of metabolically labeled lymphoblastoid cells with antibodies specific for human ferritin H-chain (αH) and L-chain (αL). (A) Control cells (C1) and Verona-1 cells (Ver-1) were metabolically labeled with³⁵S-methionine, lysed, and 2 × 10⁶ cpm of the soluble fraction of homogenates precipitated with saturating amounts of anti-H chain antibody. The soluble fraction was then precipitated again with saturating amounts of anti–L-chain antibody. The precipitates were analyzed on SDS-PAGE under denaturing conditions and exposed to autoradiography. (B) Verona-1 cells were metabolically labeled with³⁵S-methionine and immunoprecipitated as in (A), the pellets were resuspended in 4 mol/L urea, and separated on 6% polyacrylamide gels containing 4 mol/L urea under conditions that disrupt antibody antigen interactions without affecting ferritin structure. (C) As in (B), except that cells were metabolically labeled with ⁵⁹FeNTA.