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A new cold autoagglutinin specificity: the third external loop of band 3
Author(s) -
Janvier Daniel,
Lam Yin,
Galicier Lionel,
Bierling Philippe
Publication year - 2010
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/j.1537-2995.2009.02383.x
Subject(s) - cold agglutinin , antigen , antibody , autoantibody , serology , hemolytic anemia , immunology , neuraminidase , microbiology and biotechnology , medicine , chemistry , biology , virus
BACKGROUND: Cold autoagglutinins (CAs) are almost always of immunoglobulin (Ig)M class and specific for carbohydrate antigens. We report a case of hemolytic anemia caused by a mixture of IgM and IgG cold agglutinins. Both agglutinins were specific for the third extracellular loop of band 3. CASE REPORT: The patient, a 46‐year‐old man with no medical history, was admitted for an acute, life‐threatening hemolytic anemia caused by a cold agglutinin. Improvement was obtained after plasmapheresis, red blood cell (RBC) transfusions, and steroid therapy. Recovery was complete and no etiology was found. STUDY DESIGN AND METHODS: Conventional serologic procedures and immunochemical methods were used. RESULTS: The patient's autoantibody was directed to an antigen equally expressed by adult and cord RBCs, resistant to papain, neuraminidase, and endo‐β‐galactosidase treatments. This pattern of reactivity excluded all known specificities of cold agglutinins. The antibody failed to react with RBCs treated by α‐chymotrypsin or pronase, suggesting that it may be directed to the third extracellular loop of band 3. Serum fractionation showed that the cold agglutinin was composed of IgM and IgG class antibodies. Antibody specificity was confirmed by blocking tests using murine monoclonal antibodies against band 3 and by immunoprecipitation. CONCLUSION: This is to our knowledge the first observation of a CA specific for band 3. The coexistence of IgM and IgG molecules, a very unusual feature for a CA, may be related to the peptidic nature of the target antigen.