Investigation of a mild case of hemolytic disease of the newborn has l
ed to recognition of a 'new' low-incidence red cell antigen, WARR (ISB
T No. 700.55), Data gleaned from two kindreds, both with Native Americ
an heritage, exclude WARR from the MNS, Lutheran, Lewis, Duffy, Kidd,
Xg, Chido/Rodgers, Kx and Gerbich blood group systems. Serologic or ge
netic evidence suggests it is not part of the Kell or Yt systems.