Pattern of PK-R immunoreactive polypeptides in RBCs of PKD patients. Stroma-free hemolysates of a normal individual (N) and six PKD patients (no. 15, 27, 12, 29, 2a, and 2b) were subjected to isoelectric focusing in ultrathin polyacrylamide gels, and immunoreactive bands were visualized using a monospecific antibody against PK-R.5