Preferred Label : Blood group, I system;
Symbol : Ii;
CISMeF acronym : II;
Type : Phenotype, molecular basis known;
Alternative titles and symbols : I blood group system; Ii blood group system;
Included titles and symbols : Adult I phenotype;
Description : The i and I antigens of the I blood group system are carbohydrate structures carried
on glycolipids and glycoproteins and are characterized as straight or branched glycochains
composed of repeating N-acetyllactosamine (LacNAc) units, respectively. Conversion
of i antigen into an I-active structure requires the activity of the I-branching enzyme,
beta-1,6-N-acetylglucosaminyltransferase (GCNT2; 600429), which adds the decisive
GlcNAc-beta-1-6 branch onto the straight poly-LacNAc chains. Expression of the i and
I antigens on red blood cells (RBCs) is reciprocal and developmentally regulated.
Adult human RBCs predominantly express I antigen, whereas fetal and neonatal RBCs
predominantly express i antigen. After birth, I antigen levels increase gradually
as i antigen levels fall, with the normal Ii status of adult RBCs reached after about
13 to 20 months. Mutations that specifically affect 1 of the 3 variants produced by
the GCNT2 gene cause the rare adult i phenotype, in which adult RBCs are rich in i
antigen and contain low levels of I antigen. Mutations that eliminate all 3;
Inheritance : Autosomal dominant;
Molecular basis : Caused by mutation in the glucosaminyl (N-acetyl) transferase 2, I-branching enzyme
gene (600429.0004);
Prefixed ID : #110800;
Origin ID : 110800;
UMLS CUI : C0020717;
Automatic exact mappings (from CISMeF team)
- Currated CISMeF NLP mapping
- Genes related to phenotype
- Semantic type(s)
- UMLS correspondences (same concept)
