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.


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.


CONCLUSIONS
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.
Thorpe
S J
SJ
Division of Haematology, National Institute for Biological Standards and Control, Potters Bar, UK.
Boult
C E
CE
Stevenson
F K
FK
Scott
M L
ML
Sutherland
J
J
Spellerberg
M B
MB
Natvig
J B
JB
Thompson
K M
KM
D000373:Agglutinins / Q000276:immunology / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000276:immunology; D001788:Blood Grouping and Crossmatching; D003429:Cross Reactions; D003450:Cryoglobulins; D000939:Epitopes / Q000096:biosynthesis / Q000276:immunology; D005803:Genes, Immunoglobulin; D006801:Humans; D007048:I Blood-Group System / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology; D007130:Immunoglobulin Idiotypes / Q000096:biosynthesis / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000235:genetics* / Q000276:immunology; D007150:Immunohistochemistry; D007518:Isoantibodies / Q000737:chemistry; D012204:Rh-Hr Blood-Group System / Q000276:immunology*; D018029:Rho(D) Immune Globulin / Q000276:immunology / Q000378:metabolism; D001616:beta-Galactosidase / Q000494:pharmacology
D000373:Agglutinins; D000911:Antibodies, Monoclonal; D003450:Cryoglobulins; D000939:Epitopes; D007048:I Blood-Group System; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D007518:Isoantibodies; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin; C029443:cold agglutinins; D001616:beta-Galactosidase