Molecular analysis of patients with weak D and serologic analysis of those with anti-D (excluding type 1 and type 2).

Whether or not patients whose red blood cells (RBCs) carry certain weak D types produce anti-D, and if they do whether it is allo- or auto anti-D, remains controversial. The aim of this study was to determine the serologic features of anti-D in individuals expressing a weak D other than type 1 or type 2 and to assess whether the anti-D was an allo- or autoantibody. Serologic D typing and molecular analyses were performed on 748 individuals.Serologic characterization of anti-D included autologous controls,direct antiglobulin test, elution, and titration of anti-D before and after adsorption of serum onto autologous RBCs. From molecular analyses, 459 individuals exhibited a weak D type. We described seven novel RHD variant alleles. The most frequent types of weak D were type 1 (30.1%), type 2 (23.7%), type 4.0 (10.2%), type 4.2.2(20.3%), type 11 (3.9%), and type 15 (3.7%). Anti-D was identified in the sera of 9 of 47 individuals with weak D type 4.0, in 14 of 93 with weak D type 4.2.2, in 1 of 18 with weak D type 11, in 1 of 17 with weak D type 15, and in 1 weak D type 33 individual.Anti-D was demonstrated to be an alloantibody in weak D type 4.0, type 4.2.2, and type 15 individuals, but an autoantibody in weak D type 11 and type 33 individuals. In conclusion, only a complete serologic investigation of individuals with a given weak D type identified by molecular analysis allows concluding on the nature of the antibody. Transfusing weak D type 4.2.2 and type 15 patients with D- RBC units and proposing anti-D immunoprophylaxis to women with these weak D types should be considered.