Immunochemical characterization of the Rh CW antigen using human monoclonal antibodies.

BACKGROUND AND OBJECTIVES: Human monoclonal antibodies have been produced against various Rh antigens. We report here the production of another one against Rh C and the first such antibody against Rh CW. MATERIALS AND METHODS: Two heterohybridomas secreting IgG human monoclonal antibodies against Rh CW and Rh C (MS-353 and MS-242 respectively) were produced from alloimmunized donors. Their specificity was confirmed by serological testing. RESULTS: MS-353 reacted with all CW-positive phenotypes but not with any CW-negative phenotypes, whereas MS-242 reacted with all CW-positive and C-positive phenotypes. Using 125I-labelled antibodies, the average number of CW sites/red cell was 32,000 (R1WR1W, 15,200 (R1WR1), 19,800 (R1WR2), 15,300 (R1Wr), 26,200 (r'Wr), and the average number of C sites per red cell on equivalent CW/C-positive phenotypes was similar: 22,400 (R1R1), 21,800 (R1WR1), 12,300 (R1R2), 11,700 (R1WR2), 13,400 (R1r), 15,100 (R1Wr), 21,100 (r'r), 18,700 (r'Wr). MS-353 and MS-242 were mutually inhibitory. Both antibodies specifically immunoprecipitated a 33- to 34-kD polypeptide from 125I-surface-labelled cells. CONCLUSION: MS-353 is suitable for the serological detection of CW-positive cells, and the immunochemical data are entirely consistent with the report that the CW antigen is associated with a point mutation in the RHCE gene [Blood, 1995;86:1196-1201].

Cold agglutinin activity is common among human monoclonal IgM Rh system antibodies using the V4-34 heavy chain variable gene segment.

BACKGROUND: The V4-34 gene segment is commonly used by human monoclonal IgM alloantibodies against blood group antigens and by cold-reactive red cell autoantibodies with anti-I or anti-i specificity. This study was conducted to determine whether cold agglutinin activity is found among the V4-34-encoded alloantibodies. STUDY DESIGN AND METHODS: Fifty-four human IgM monoclonal antibodies (MoAbs) against Rh system antigens were tested for cold agglutinin activity against red cells lacking the relevant Rh system antigen and for reactivity with tissue I and/or i antigens using immunohistochemistry. The findings were correlated with the utilization of the V4-34 segment as determined in an enzyme-linked immunosorbent assay with an antibody (9G4) that is specific for this gene product and were also correlated with other serologic properties. RESULTS: Of the MoAbs, 59 percent were 9G4-positive. Of the 9G4-positive subset, 16 and 44 percent agglutinated native adult (express I) and cord (express i) cells, respectively, at 4 degrees C; these levels rose to 84 and 94 percent, respectively, with the use of papain-treated cells. The red cell antigens recognized at 4 degrees C were cleaved by endo-beta-galactosidase, which is consistent with their being I and i. Of the 9G4-positive subset, 53 percent bound to tissue i antigen. These reactivities were not found among 9G4-negative MoAbs. Endo-beta-galactosidase treatment of red cells enhanced Rh system antibody agglutination by 9G4-negative MoAbs. CONCLUSION: Anti-I/i reactivity is common among IgM Rh system MoAbs and is shown only by the V4-34-encoded subset. This finding has implications for the use of MoAbs for Rh system typing of blood.