Relationship of involved amino acid position, antigen density, and Rhesus index.

A model for the orientation of the RhD protein in the red-cell membrane is shown.26 The amino acid positions involved and their effect on antigen density (A) and on Rhesus index (B) are indicated for 15 weak D and 3 partial D alleles with single missense mutations. Symbols denote major changes (▴, antigen density less than 500 RhD antigens/cell or Rhesus index less than 0.2, respectively), moderate changes (•, 500-2000 RhD antigens/cell; Rhesus index, 0.2-0.6), and minor changes (○, more than 2000 RhD antigens/cell; Rhesus index more than 0.6). RhD antigen density was too low for the determination of the Rhesus indices in 2 weak D types (Δ, weak D type 12 and type 17).