Matuhasi‐Ogata Phenomenon Involving Anti‐Ampicillin

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Abstract
A 47 yr old group A, Rh1Rh1 woman treated with i.v. ampicillin for chronic pyelonephritis received 2 units of blood and also received oral cephalexin. Three months after the transfusions she was noted to have allo-anti-E and anti-c, and a 2+ positive direct antiglobulin test. Anti-E and anti-c could be eluted from her cells, yet neither antigen could be demonstrated on the patient''s circulating red blood cells. Also present in the serum and in the eluate was anti-ampicillin antibody. Studies of the patient''s red blood cell eluates using ampicillin-treated R1R1 and untreated R2R2 cells demonstrated anti-E complexed with anti-ampicillin in a drug-related example of the Matuhasi-Ogata phenomenon. Artificially created mixtures of anti-E and drug antibody could reproduce the effect in vitro. No effect of cephalexin could be demonstrated. The variability of the Matuhasi-Ogata phenomenon is discussed with regard to the sequence of antibody attachment, and the possible relationship to cephalexin is discussed. Drug antibodies may be involved in the Matuhasi-Ogata phenomenon in cases where another red blood cell antibody cannot be shown to be present.