Gu, a Variant of G

G^u, analogous to D^u and E^u, is a weak variant of G appearing in a haplotype lacking C, D, and E but having e^s.
In a preliminary survey, the red blood cells ot three of 186 Negro blood donors found negative when tested for C, D (incuding D^u), and E were shown to be G^u-positive when tested with anti-CD by the antiglobulin technic.
Fourteen additional examples from unrelated persons and five members of a family have been investigated in this study. All G^u-positive individuals tested are VS-positive, but V-negative, and all are Negro. Although G cells show greater antibody uptake when used to absorb anti-CD, G^u cells elute anti-G in substantially greater amounts than do G cells. Comparative studies demonstrate similarity of specificity but a difference of avidity, which could be due to the influence of e^s(VS) in cis position.
G^u-positive bloods have been shown to stimulate the production of anti-G in Rh-negative recipients. The test for G^u can be incorporated in the test for D^u by substituting anti-CD or anti-CDE for anti-D serum.