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, DHMi and DHMii. DHMi was characterised by a negative reaction with BRAD-8 and DHMii by a negative reaction with BRAD-5. DHMi cells were found to have a papain-sensitive site, identified by Mab 21 G6, which was not detectable in DHMii. The presence of allo-anti-D in one case of DHMi suggests a partial D in these individuals. The positive reaction of HAM-A with sialidase- and endo-F-treated DHMii 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 DHMi cells tested, but not with DHMii cells. Data from family studies suggest that the variant D in both DHMi and DHMii is inherited as a cDE gene complex and is controlled by the RH locus.