[Anti-M after transfusion as an indication of a genetic variant of the MN locus]

Abstract

We report a case of an anti-M antibody (titer 128) and MN red blood cells (RBC) in a 76-year-old female German patient. In our case, however, RBC showed weak reactions to human anti-M compared with strong reactions using rabbit anti-M. Papain treatment destroyed the RBC reactivity to human anti-M whereas the strong reactivity to rabbit anti-M was unchanged. This pattern was also demonstrable in the patient's son and grandson. Our results indicate the existence of a rare allele at the MN locus in this family.