A new phenotype in the Ii blood group system

I-i- phenotype in a large kindred Indian family

The I-i- phenotype was found to be a familial character up to three generations in a large Indian family having 93 members. 15 members showed highly depressed Ii antigens while 6 of the members had partial depression of the Ii antigens on their red cells. It was evident in the family that the phenotype is associated with A1 antigen. The A1 antigen score on the red cells was significantly higher among the subjects with depressed Ii antigens. The I-i- status was not considered as a dominant or a recessive character nor does the partial depression of the Ii antigens indicate a heterozygous state of the variant gene.

Subtypes of i demonstrated by the use of atypical Ii cell types and inhibition studies

Haemagglutination, absorption and elution studies with several anti-i sera and atypical Ii red cell types and Oh cells were carried out and three subtypes of specificity were demonstrated. The fourth i subtype was demonstrated by an inhibition method using human serum and amniotic fluid as a source of i substance.

A new red cell phenotype I-i-: red cells lacking both I and i antigens

When blood samples from 5,864 healthy Indian blood donors were tested with anti-I, seven samples failed to react or reacted only weakly. Further studies with a number of anti-I and anti-i sera suggested that these samples had the phenotype I-i- and reacted weakly with anti-IT. In one family, the I-i- phenotype was present in three generations.