The effect of trypsin on the duffy factor.

Abstract

Abstract The Duffy antibody cannot be detected by saline agglutination, albumin-plasma, or trypsinated cell methods. If untreated Fy(a+) cells are used for the test, the indirect antiglobulin test is the only known method to detect the Duffy antibody. If Fy(a+) cells, treated either with trypsin, papain, or ficin are used, they not only fail to be clumped but they also can no longer be coated with their specific antibody as evidenced by a negative indirect antiglobulin test. Trypsin-treated Fy(a+) cells and untreated Fy(a−) cells appear to react in the presence of anti-Fy a in like fashion. Absorption experiments show that untreated Fy(a+) cells can completely absorb Fy a antibodies from immune serum, whereas the same cells treated with trypsin have completely lost this ability. Antiglobulin tests carried out on the untreated cells used for the absorption experiment are strongly clumped, whereas trypsin-treated cells used in the same manner show no clumping whatsoever. Treatment of Duffy positive cells with enzyme interferes with their expected reaction with specific antibody. This is not mechanical in nature because after repeated washing of Fy(a+) cells with normal saline, the intensity of the indirect antiglobulin test using anti-Fy a remains unchanged. Evidence favors the conclusion that enzyme acts directly on this hemoagglutinogen and renders it unable to react with its specific antibody and that this reaction is quite independent of its action on the Rh 0 factor. This is in direct contrast to the results obtained with trypsinated Rh 0 -positive cells, the agglutinability of which, by sera containing Rh 0 univalent antibodies is increased. Although the trypsin-treated cell method is of great value and the trypsinated cell indirect antiglobulin method detects antibodies in such low titer that all other methods fail, yet these methods must not be relied upon to detect the Duffy antibody. If enzyme-treated cells are used for crossmatch test preliminary to transfusion or for a screening test to diagnose sensitization, failure to detect anti-Fy a will result unless in addition the indirect antiglobulin test using untreated cells is carried out.