Classification of subjects with a partial D antigen is traditionally performed with immune anti-D sera. The development of monoclonal antibodies enables a fine analysis to be made of the specificity of the epitopes that are present or missing in these cases. A systematic search in a Caucasian donor population of 17,500 revealed 8 unrelated male individuals (frequency 0.05%) with a red cell phenotype characteristic of partial D category VI, but without anti-D in their serum. The relation to the ‘classic’ partial D category VI was investigated and is discussed, as is the observed serological heterogeneity of the partial D category VI group. Clinical consequences for the prevention of immunization of these subjects are mentioned.
In 1987 the definition of an Rh-negative donor in the Netherlands was changed from C-, E- as well as
D^u-negative to D-negative only. The use of 2 different strong anti-D sera without an antiglobulin phase (D^u test) was
considered sufficient to reveal the clinically important D antigen. In applying this policy, we identified 32 donors in
13,500 consecutive blood donations whose indirect antiglobulin test (IAT) (D^u)-positive red cells gave negative
reactions with at least 2 out of 11 anti-D sera and whose cells might therefore be typed as Rh(-D-)-negative in routine
investigations. IgG anti-D used by a one-stage bromelain technique and anti-D with modified IgG appeared to be
relatively insensitive in detecting D^u in this study. Polyclonal anti-D in an enhancement medium and monoclonal
anti-D scored better, although differences exist between the products of various manufacturers. It is suggested that if
IAT (D^u) testing is omitted, only anti-D sera with a high index of detectability of cells expressing weak D antigens
should be accepted.
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