Immunoblots of membrane proteins from erythrocytes and organs. Membranes were prepared as explained in Materials and Methods and the detergent soluble proteins were run in SDS-PAGE minigels, electrotransferred onto nitrocellulose membranes, and immunoblotted with antibody Fy6 at a dilution of 1/500 (A) and antibody 6615 at a dilution of 1/5000 (B). The antibodies were detected by chemiluminescence using the ECL Western blotting procedure as explained by the manufacturer (Amersham Life Science, Arlington Hts, IL). (A) Erythrocytes of a Duffy-negative individual (lane 1), erythrocytes of a Duffy-positive individual (lane 2), adrenal tumor of a Duffy-negative individual (lane 3), colon of a Duffy-negative individual (lane 4), colon of a Duffy-positive individual (lane 5), kidney of a Duffy-positive individual (lane 6), and spleen of a Duffy-positive individual (lane 7). Aliquots of 10 μg of erythrocyte membrane proteins and 60 μg of organ membrane proteins were analyzed per lane. (B) Erythrocytes of a Duffy-negative individual (lane 1), erythrocytes of a Duffy-positive individual (lanes 2 and 3), adrenal gland (lane 4), adrenal tumor of a Duffy-negative individual (lane 5), colon of a Duffy-negative individual (lane 6), colon of a Duffy-positive individual (lane 7), kidney of a Duffy-positive individual (lane 8), thyroid of a Duffy-positive individual (lane 9), spleen of a Duffy-positive individual (lane 10). For the negative control the spleen of a Duffy-positive individual was immunoblotted with preimmune serum and with a second antibody (not shown). A 25-μg aliquot of erythrocyte membrane proteins was analyzed in lanes 1 and 2 and a 2-μg aliquot of erythrocyte membrane proteins was analyzed in lane 3. A 60-μg aliquot was analyzed in each lane of membrane protein of tissues.