Identification of Two New D Variants, DHMi and DHMii Using Monoclonal Anti-D

Fifteen examples of red cells are described which showed discrepant reactivity on routine grouping with two monoclonal anti-D typing reagents, HAM-A being negative and MAD-2 strongly positive. The reaction profile of these cells with a number of monoclonal anti-D characterised the samples into two new variant groups, D^HMi and D^HMii. D^HMi was characterised by a negative reaction with BRAD-8 and D^HMii by a negative reaction with BRAD-5. D^HMi cells were found to have a papain-sensitive site, identified by Mab 21 G6, which was not detectable in D^HMii. The presence of allo-anti-D in one case of D^HMi suggests a partial D in these individuals. The positive reaction of HAM-A with sialidase- and endo-F-treated D^HMii cells suggests that sialic acid and/or N-glycans could possibly be involved in blocking the reaction with untreated cells. All samples typed as C-E+. One was e negative while the rest had variable depression of the e and f antigens. Marginal depression of E was seen with those D^HMi cells tested, but not with D^HMii cells. Data from family studies suggest that the variant D in both D^HMi and D^HMii is inherited as a cDE gene complex and is controlled by the RH locus.