Fig. 4. Unassembled TCRα associated with a KDEL protein, BiP. HeLa cells were transiently transfected with TCRα, and then lysed and immunoprecipitated with an anti-murine TCRα mAb (A2B4) followed by SDS–PAGE. The membrane was immunoblotted using mouse anti-BiP mAb (SPA-827), which also recognizes GRP94, or a rabbit anti-murine TCRα antiserum. Immunoprecipitates from cells transfected with TCRα contained BiP, not GRP94 (a-TCRα IP). Direct immuno blotting of cell lysates (wl) revealed similar levels of BiP and GRP94 in either transfected (TCRα Tf) or non-transfected cells (Non Tf).