DBT: a partial D phenotype associated with the low‐incidence antigen Rh32

Abstract

Eight probands are described with a D phenotype in which a partial D antigen is associated with Rh32 antigen; three of these probands were investigated because of the anti-D in their serum. The partial D lacks epD1-epD5 and epD9 and some epD6/7 and only expresses epD8 and other parts of epD6/7. The strength of the partial D antigen varies between unrelated DBT individuals. The Rh32 antigen of the DBT cells is weaker than that of D(C)(e) cells. Tests on DBT, DFR and R0Har cells with anti-epD6/7 split these monoclonal anti-D into eight patterns of reaction. A new pattern of reactions was observed, presaging a new epitope, but this was not numbered.

Variants of RhD – current testing and clinical consequences

“…Anti‐D in women with variant D red cells have been responsible for severe HDFN. Some cases, severe enough to warrant exchange transfusion and one leading to fetal death, have been published and involve mothers with DIIIa (Beckers et al , ), DIVb (Okubo et al , ), DVI (Lacey et al , ), and DBT (Wallace et al , ), and D variants described as D U (Hill et al , ; White et al , ), ‘D+’ (Østgård et al , ), and Rh B (Lowes, ). Although I am not aware of any report of anti‐D in a D variant patient causing a haemolytic transfusion reaction, D variant patients with anti‐D should be transfused with D− red cells.…”

A D+ blood donor with a novel RHD*D‐CE(5‐6)‐D gene variant exhibits the low‐frequency antigen RH23 (DW) characteristic of the partial DVa phenotype

“…RBCs from this hybrid allele express a partial RhD phenotype lacking D Epitopes 1.2 and 5.1 and are RH23 (D W )+, Rh32–. Rh32 is expressed by DBT‐1 and DBT‐2 encoded by RHD*D‐CE(5‐7)‐D and RHD*D‐CE(5‐9)‐D, respectively . The absence of Rh32 antigen in our propositus suggests that interaction of polypeptides encoded by RHD Exon 4 and RHCE Exons 5 and 6 alone is not sufficient to express Rh32 and the latter requires RHCE Exon 7.…”

“…Formation of these LFAs is thought to be due to the interaction of amino acids encoded by RHD Exon 4 and RHCE Exon 5 . DV and DBT cells are defined by two distinct characteristic patterns of reaction against a panel of anti‐D MoAbs …”

Rh and RHAG Blood Group Systems

“…Rh32 is a low frequency antigen associated with the partial D antigen DBT [184] and with the R N complex, which has normal D, but weak C and e (Section 5.14.1.1 ). Of eight DBT propositi tested, fi ve had normal C and c, two had weak C (one of whom had a weak e), and one was C − c + .…”