Micromethod for MN antigen grouping of dried bloodstains

A micromethod based on the absorption elution technique was shown to be applicable to the detection of M and N blood groups of dried bloodstains on cotton cloth. Each antigen M and N was tested using two different types of antisera. Two hundred different bloodstains, stored up to six months, were analyzed. Conclusive results were obtained for M typing on 2.5-mm-long bloodstained threads. For N typing, some cross-reactivity of homozygous M stains with anti-N sera was observed. This may be explained by the structure of the M and N antigens on the red cell membrane.