Unusual reactivity of several anti-U serums with red cells from RN persons

Several examples of anti-U were diluted serially and tested with RN red cells and red cells of various Rh phenotypes from both blacks and whites. The agglutination scores were reduced for U+ red cells from people with RN compared with U+ red cells from whites. U+ red cells from blacks yielded score values greater than red cells from people who inherited RN, but definitely less than U+ red cells from whites. The rank-correlation coefficient (0.92) indicated a p value of 0.0005.