Anti-ovalbumin monoclonal antibodies interact with their antigen within the internal membranes of Xenopus oocytes.

The microinjection of selected antibodies into the cytosol or nucleus of living cells is proving a useful technique for investigating the function of intracellular proteins1-5. The rationale underlying this approach is that, in binding to its antigenic determinant, the antibody may mask or disrupt the activity mediated by the region of the protein near the determinant. This technique, however, cannot be used to identify functions related to antigenic determinants of proteins within the lumen of the endoplasmic reticulum (ER), or Golgi compartments, since both regions are inaccessible to direct microinjection and since the movement of proteins into these areas from the cytosol occurs during but not after their translation6. In theory, this constraint could be overcome if the mRNAs specifying the antibody were injected into the cell containing the target antigenic determinant. After the vectorial and co-translational transfer of its constituent chains through the membrane, the antibody would then be assembled within the lumen of the ER thereby being in a position to bind to its antigenic determinants. We demonstrate here a successful example of such an approach. © 1982 Nature Publishing Group.