At least 14 iodinated proteins can be distinguished by SDS polyacrylamide gel electrophoresis followed by autoradiography in the membrane of intact human neutrophils. Neutrophils from patients suffering from rheumatoid arthritis show a modified expression of 4 outer membrane proteins. Three polypeptide components of the 30, 50 and 130 K were decreased by 95%, while the 120 K component dramatically increased. The possible relationship between the altered cell sensitivity and the defective expression of membrane proteins is discussed.